Migraine headache is one of the

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1 CLINICAL DECISION MAKING Simplifying the Diagnosis of Migraine Headache Vincent T. Martin, MD ABSTRACT Migraine headache is a very common disease encountered by primary care physicians. Its prevalence is 12% in the general population but may approach 57% to 76% in those presenting with a complaint of headache in the primary care setting. Primary care and specialty physicians alike misdiagnose migraine headache. It is more likely to be misdiagnosed in those with multiple headache types, comorbid psychiatric illnesses, and frequent headache. The International Headache Society has proposed criteria for the diagnosis of migraine and other headache disorders, but they have had poor utilization within primary care. Therefore, abbreviated diagnostic criteria have been developed to aid physicians in the diagnosis of migraine headache. The presence of nausea, vomiting, photophobia, or moderate to severe disability (any one of these) has a high positive predictive value for the diagnosis of migraine headache. The following article presents an informed approach to the diagnosis of migraine within primary care. (Adv Stud Med. 2004;4(4): ) See editorial on page 208. See Tables A, B, C, and Appendix at end of article. Migraine headache is one of the most common disorders encountered by primary care physicians. Associated with significant morbidity, migraine headache is more prevalent than diabetes, hypertension, and asthma (Figure 1). 1,2 A recent World Health Organization survey placed severe migraine headache in the highest disability category along with quadriplegia, dementia, and schizophrenia. 3 However, migraine is diagnosed in less than half of all patients despite its prevalence and impact. 4 The following article presents a simplified approach to the diagnosis of migraine headache for use within primary care. PREVALENCE Migraine headache affects 12% of the United States population and is 3 times more common in women than in men. Women often experience migraine during their peak reproductive years, with a prevalence of 20% to 30% between the ages of 30 and 50 years. 2 The prevalence of migraine is significantly higher in patients from primary care practice sites than within the general population. A recent US study screened patients (regardless of complaint) in primary care physicians waiting rooms and found 29% met diagnostic criteria for migraine headache. 5 The probability of migraine increases further in those with a chief complaint of headache. A study from a Seattle-based health maintenance organization reported a prevalence of migraine headache of 57% in those presenting to their primary care physician with a complaint of headache. 6 Another international study discovered a prevalence of migraine in 76% of primary care patients with a complaint of episodic headache (<15 days per month); these were patients in whom the physician did not suspect a secondary cause. 7 Dr Martin is Associate Professor of Medicine, Division of General Internal Medicine, University of Cincinnati. Dr Martin has reported he is a consultant for and receives honoraria from AstraZeneca Pharmaceuticals LP; GlaxoSmithKline; Johnson & Johnson; Merck & Co, Inc.; and Pfizer Inc. Off-Label Product Discussion: The author does not include information on off-label use of products. Correspondence to: Vincent T. Martin, MD, University of Cincinnati, Division of General Internal Medicine, 231 Albert Sabin Way, Rm 6603, Cincinnati, OH Vol. 4, No. 4 April 2004

2 MIGRAINE HEADACHE The spectrum of migraine prevalence ranges from 12% in the general population to between 57% and 76% in those presenting with a complaint of headache in the primary care setting. Therefore, in the absence of red flags for a secondary headache disorder (discussed below), migraine should be considered the most probable diagnosis in the patient who presents to the primary care physician with a headache complaint. MEDICAL CONSULTATION FOR MIGRAINE Family practitioners, general internists, and pediatricians provide medical consultation for the vast majority of migraine patients. Lipton reported that primary care physicians were the first to diagnose migraine headaches in 58% and 62% of female and male patients, respectively. 8 Primary care physicians also were the most frequent providers of follow-up care for 58% of women and 54% of men with migraine. By contrast, neurologists and headache specialists accounted for only 14% and 10% of the follow-up care for male and female migraineurs, respectively. UNDERDIAGNOSIS The American Migraine II study reported that physicians had previously diagnosed only 48% of those meeting diagnostic criteria for migraine. 3 Seventy-seven percent of the undiagnosed group reported substantial disability with their migraine headaches. 9 This lack of diagnosis is not solely attributable to the physician, as 31% of patients had never sought medical care for a complaint of headache. The remaining 69% had consulted a physician, but approximately one third of these patients subsequently lapsed from medical care. Patients reported the following reasons for lapsing from medical care: (1) headaches less severe or less frequent, (2) ineffective treatment, (3) nothing a doctor can do, (4) physician did not help me, and (5) physician not interested in headaches. 8 MISDIAGNOSIS Approximately 50% of patients with a final diagnosis of migraine initially had received a nonmigraine diagnosis from primary care physicians in a Seattle-based health maintenance organization. 6 An international study of primary care physicians reported a misdiagnosis rate of 25% in patients with migraine headache. 10 With misdiagnosis rates ranging between approximately 25% to 50%, in patients who initially receive a diagnosis of nonmigraine headache, primary care physicians should be particularly attuned to the possibility that an initial diagnosis of nonmigraine headache may be incorrect. Stang reported the positive and negative predictors of a diagnosis of migraine headache by primary care physicians. 6 Female sex, the presence of aura, and higher pain severity significantly increase the likelihood of a diagnosis of migraine. The most significant negative predictor is the coexistence of migraine and tension-type headaches in the same patient. 11 Physicians will often ask the patients to describe the headaches during the diagnostic interview, and the patient will report symptoms of both headache types, which confuses the diagnostic picture. In this situation, the physician can tease out a diagnosis of migraine headache by asking patients to describe their most severe headaches. Age may also be a negative predictor; however, secondary causes of headache must be ruled out before making a new diagnosis of migraine in a geriatric patient. PITFALLS IN DIAGNOSIS The location of head and neck pain also may lead to confusion in the diagnosis of headache. For example, a complaint of bilateral headache often sways a physician to diagnose tension-type headache, but migraine headache can be bilateral in 25% to 48% of patients. And, whereas neck pain is perceived to be commonly associated with tension-type headache, it may occur in 70% of migraineurs; two thirds describe it as tightening and 43% have bilateral neck pain. Therefore, the presence of bilateral headache or neck pain should not dissuade one from diagnosis of migraine. 12 Depression and anxiety can also cloud the diagnosis of migraine headache. Another pitfall is that primary care physicians frequently accept the patient s self-diagnosis of headache. This may, in part, relate to a misinterpretation of the meaning of tension-type headache by the patient Figure 1. Prevalence of Common Diseases Among Patients in Primary Care Settings* *The prevalence of diabetes, hypertension, and asthma are for those 45 years of age and younger. Data from Benson et al 1 and Lipton et al. 23 Advanced Studies in Medicine 201

3 CLINICAL DECISION MAKING and physician alike. It is commonly believed that all headaches triggered by stress and/or psychiatric illness represent tension-type headaches. 11 Yet, stress is one of the most commonly reported triggers for migraine, and psychiatric illnesses such as depression and anxiety commonly accompany migraine. 13 Also, a patient s self-diagnosed sinus headache commonly represents migraine headache. Cady recruited 47 consecutive patients from primary care and specialty clinics who had a history of 6 self-described sinus headaches within the prior year. 14 Ninety-eight percent of those with self-diagnosed sinus headache fulfilled criteria for migraine or migrainous (lacking 1 diagnostic criterion for migraine headache) headaches. BARRIERS IN THE PRIMARY CARE SETTING Barriers to establishing a diagnosis of migraine headache exist in the primary care setting. The most important barriers are the length of the office visit and the number of complaints addressed by the primary care physician during the visit. Mean visit lengths in primary care practices vary from 8 to 15 minutes in the United Kingdom 15 to 11 to 15 minutes in the United States. 16 A typical primary care patient often presents with multiple complaints, a factor that may preclude assigning causal relationships with any certainty and limits therapeutic options. The primary care physician must assess the relative seriousness of these concerns and in collaboration with the patient determine what if any treatment should be pursued. These issues may leave some complaints unexplored either inadvertently or by agreement. A lack of awareness of the International Headache Society (IHS) diagnostic criteria for migraine headache may constitute another barrier to diagnosis in primary care. Primary care physicians most commonly code headaches that fulfill validated criteria for migraine as Headache NOS (Headache Not Otherwise Specified), and many may not be convinced that a more specific diagnosis serves the patient unless it will change how the patient s care is managed. 17 Under the current IHS classification system, a headache must meet 7 criteria and clinicians must ask at least 9 questions to establish a diagnosis of migraine without aura. For migraine with aura, an additional 4 criteria must be met. CURRENT IHS CRITERIA The IHS first developed criteria for the diagnosis of headache disorders in 1988, and these were later revised in They were initially developed to standardize the diagnosis of headache disorders within the context of clinical research studies. Migraine headache was classified into those with and without aura (formerly called classic and common migraine, respectively). It was considered episodic if the headache occurred <15 days per month and chronic if 15 days per month. Headaches were also classified as probable migraine if they lacked 1 diagnostic criterion. The IHS diagnostic criteria for migraine with and without aura are discussed below. MIGRAINE WITH AURA Migraine with aura constitutes 15% to 30% of all patients with migraine headache. The IHS criteria for migraine with aura are listed in the sidebar. The aura of migraine headache is a focal neurologic symptom that develops gradually and lasts for 5 to 60 minutes. The aura may be categorized as visual, sensory, or motor. Visual aura is the most common, and its symptoms include flashing lights or spots, zigzag lines, scotomata, and loss of vision. The symptoms of sensory aura include numbness or paresthesias, and those of motor aura include hemiparesis or hemiplegia. The aura is generally accompanied by a headache that begins during the aura or within 1 hour after the aura abates. The headache is indistinguishable from that of migraine without aura. Rarely, the aura may occur without headache. Migraine with aura can be further subcategorized into those having typical aura (visual/sensory symptoms and/or dysphasic speech) and hemiplegic aura (motor symptoms). MIGRAINE WITHOUT AURA Migraine without aura accounts for 70% to 85% of all patients with migraine headache. Characteristics of the headache include: (1) unilateral location, (2) moderate to severe intensity, (3) throbbing quality, and/or (4) worse with physical exertion. Its most differentiating features, however, are the associated symptoms of nausea/vomiting and photophobia/phonophobia. The headaches generally last 4 to 72 hours and have no preceding aura. The IHS criteria for migraine without aura are listed in the sidebar. PROBLEMS WITH THE IHS CRITERIA The IHS criteria for migraine headache have not experienced broad clinical use within primary care. A recent study of the use of the 1988 version of the IHS criteria in 9 headache centers demonstrated that even headache specialists experienced difficulty applying them in up to one third of patients. 19 The criteria have been criticized as being too complex, lengthy, and cumbersome for routine use in clinical practice. They also do not distinguish which features are most helpful in establishing or excluding a migraine diagnosis. These deficiencies in current IHS criteria have led to the development of abbreviated migraine diagnostic criteria. 202 Vol. 4, No. 4 April 2004

4 MIGRAINE HEADACHE IHS Criteria for Migraine Headache With Aura 18 A. At least 2 attacks fulfilling criteria B through D B.* Aura must be fully reversible and consist of at least 1 of the following symptoms: Visual Sensory Dysphasic speech C. At least 2 of the following: Homonymous visual symptoms and/or unilateral sensory symptoms Aura symptoms develop gradually over >5 minutes and/or different aura symptoms occur in succession over 5 minutes Each aura symptom lasts >5 minutes and <24 hours D. Headache begins during the aura or follows the onset of aura within 60 minutes E. Not attributed to another disorder IHS Criteria for Migraine Without Aura 18 A. At least 5 attacks fulfilling criteria B and C B. At least 2 of the following characteristics: Unilateral Throbbing Moderate to severe intensity Worse with exertion C. Headache must be accompanied by 1 of the following symptoms: Nausea or vomiting Photophobia and phonophobia D. No signs of a secondary headache disorder E. The headache lasts 4-72 hours. *These are the clinical features of typical aura with migraine headache under the new diagnostic criteria. If the patient has hemiplegia as the aura symptom, the headaches are termed hemiplegic migraine. IHS = International Headache Society. Adapted from the Subcommittee IHS. The International Classification of Headache Disorders 2nd Ed. Cephalalgia, with permission from Blackwell Publishing. ABBREVIATED DIAGNOSTIC CRITERIA Studies of abbreviated diagnostic criteria have been reported in the literature with the intent of simplifying the diagnosis of migraine headache. These studies must be interpreted critically, since the study design differed among the studies. First, they were often conducted in different patient populations (specialty practices vs primary care), which could affect their generalization to primary care. Second, the definitions of clinical variables for the abbreviated criteria may have varied across studies. For example, nausea could be elicited by asking any of the following questions: (1) Are you nauseated with your headaches? (2) Do you want to eat when experiencing a headache? (3) Are you sick to your stomach with your headaches? (4) Are you queasy with your headaches? Third, some studies used a diagnostic interview to develop their abbreviated criteria and others used a self-administered questionnaire. Studies have suggested poor agreement between the results of selfadministered questionnaires and diagnostic interviews. 20 Fourth, some studies used IHS criteria as the gold standard for the diagnosis of migraine, whereas others used older criteria developed prior to Fifth, nonmigraine headache was defined differently across the studies. Most considered all other headaches to be nonmigraine, whereas some considered only tension-type headaches nonmigraine. Also, few models of abbreviated criteria have been validated in a second population to ascertain the transportability of the models. Those models using IHS criteria as the gold standard for the diagnosis of migraine are reviewed below. ABBREVIATED MODELS: ASSESSMENT OF PREDICTIVE VALUE Bayes theorem can be used to evaluate the predictive value of the various abbreviated models for the diagnosis of migraine headache. The theorem states that the pretest odds of disease multiplied by the likelihood ratio (LR) of the diagnostic test represents the posttest odds of disease. (For a brief overview of the operating characteristics of diagnostic tests, please refer to the Appendix for this article, located at the journal s Web site, A high positive LR (used if the diagnostic test is positive) significantly increases the likelihood of migraine headache, whereas a low negative LR (used if the diagnostic test is negative) significantly decreases the likelihood of disease. Therefore, a high positive LR helps rule in the diagnosis of migraine headache, and a low negative LR helps rule out the diagnosis. Abbreviated models with positive LRs >3 increase the probability of migraine to >70% in those presenting to their physicians with a complaint of headache. Similarly, abbreviated models with negative LRs <0.3 decrease the likelihood of migraine to <30%. These thresholds are used to evaluate the predictive value of the abbreviated models discussed below. MODELS USING 1 VARIABLE Four past studies have reported the performance of single-variable models in the diagnosis of migraine headache using IHS diagnostic criteria. Three of the 4 studies included a diagnostic interview 21,22 and 1 study included a self-administered questionnaire. 23 The patient groups were obtained from community and clinic-based samples Nausea, vomiting, and photophobia have positive LRs >3, suggesting good positive predictive value in the diagnosis of migraine headache. Negative predictors of migraine (negative LRs <0.3) were nausea, pho- Advanced Studies in Medicine 203

5 CLINICAL DECISION MAKING tophobia, and moderate to severe headache. This indicates that the absence of these variables significantly reduces the probability of migraine headache. MODELS USING MULTIPLE VARIABLES There have been 3 past studies of abbreviated diagnostic criteria with multiple variables using IHS criteria as the gold standard for the diagnosis of migraine headache. Two of the abbreviated diagnostic criteria were developed through use of a self-administered questionnaire 23,25 and 1 through the use of a diagnostic interview. 26 Only the model by Lipton was both developed and validated within a primary care population. 23 The models of Lipton et al 23 and Pryse-Phillips et al 25 maintained good positive and negative LRs (>3 and <0.3, respectively), whereas that of Solomon et al 26 had a good negative LR but a fair positive LR. Therefore, only the models of Lipton et al and Pryse-Phillips et al are discussed below. Lipton developed a 3-item self-administered questionnaire to screen for migraine, called ID Migraine. 23 His initial patient population was recruited from the waiting rooms of primary care physicians. Participants were enrolled if they answered yes to 1 of the 2 following questions: (1) Have your headaches limited your ability to work, study, or enjoy life? (2) Do you want to speak with a healthcare professional about your headaches? All participants completed a 9-item self-administered questionnaire of IHS criteria in the offices of their primary care physician and were later referred to a headache specialist, who made the diagnosis. The questions regarding Figure 2. The ID Migraine Questionnaire *An affirmative response on 2 of 3 questions yield a sensitivity and specificity of 81% and 75%, respectively. ID Migraine should be used in conjunction with a comprehensive clinical evaluation in order to make the diagnosis of migraine. Adapted with permission from Lipton et al. 23 nausea, photophobia, and disability were the most predictive for a diagnosis of migraine headache, with adjusted odds ratios of 3.9, 3.8, and 3.3, respectively. An abbreviated questionnaire, the ID Migraine Questionnaire, was then developed using these 3 questions (Figure 2). If participants answered 2 of the 3 questions affirmatively, the positive and negative LRs were 3.2 and 0.25, respectively. The internal consistency of the 3- item questionnaire was high, and the operating characteristics of the model remained similar in clinically relevant subgroups (eg, different age groups and genders, those with and without a previous diagnosis of migraine). This questionnaire was later validated in a second sample of primary care patients. Pryse-Phillips and a group of Canadian neurologists 25 also developed a 3-item questionnaire to diagnose migraine headache. The initial study population (n=476) included patients who had entered prior clinical trials and those who had definite diagnoses of migraine headache, tension-type headache, and other headache disorders, recruited from 5 neurology practice sites. All patients completed a 96-item self-administered questionnaire designed to ascertain the characteristics and precipitants of their headache disorder. The following 3 questions were most predictive for a diagnosis of migraine headache: (1) Do you have a headache every day? (2) Is your headache on 1 side of the head only? (3) Does your headache stop you from doing things? (The questions were asked sequentially; patients answering affirmatively on question 1 were considered to have nonmigraine headaches; patients responding negatively to question 1 and affirmatively to questions 2 or 3 were considered to have migraine headaches. This 3-item questionnaire had a positive LR of 3.2 and negative LR of 0.2 in a separate validation study involving 100 patients. In the validation study, the participating physicians verbally administered the questionnaire. MODELS OF DISABILITY Headache specialists frequently state, Disabling headache is migraine until proven otherwise. The truth of this assertion depends on the definition of disability. Lipton used the following question to quantify disability in his study: How many days did your headaches limit you from working, studying, or doing what you needed to do? He reported a positive LR and a negative LR of 1.8 and 0.25, respectively, for patients with 1 day or more of disability in the last 3 months from their headaches. 23 Another study by Lipton et al found that any disability (mild, moderate, or severe) had a sensitivity of 85% in the diagnosis of migraine headache. 27 Maizels et al reported a positive LR of 2.3 and a negative LR of 0.24 for a single question addressing whether the patient experienced severe or disabling episodic headache Vol. 4, No. 4 April 2004

6 MIGRAINE HEADACHE Therefore, a negative response to a question asking about any impact or disability of headache appears to rule out migraine (LR <0.3), but a positive response does not rule it in. The HIT-6 is a 6-item questionnaire designed to identify the degree of impairment of migraine headache. 29 The response to each question is scored and later summed to provide a total score (range of scores 36-78), with higher scores indicating higher levels of disability. The HIT-6 has also been studied as a diagnostic tool for migraine headache. Ware et al reported that the positive LR increases as the total score of the HIT-6 increases. These data would suggest that the presence of moderate to severe disability significantly increases the probability of a migraine headache diagnosis. Figure 3. Clinical Approach to Diagnosis and Treatment of Migraine Headache CLINICAL APPROACH TO DIAGNOSIS AND TREATMENT Clearly a need exists to develop a simplified approach to the diagnosis and treatment of migraine headache in primary care. This approach would involve 3 steps (Figure 3). STEP 1: EXCLUDE SECONDARY CAUSES OF HEADACHE The mnemonic SNOOP has been developed to remember secondary causes of headache (eg, brain tumor, subarachnoid hemorrhage, etc) (Table). Secondary causes of headache remain of great concern to primary care physicians. Despite such concern, they occur infrequently in primary care patients complaining of headache. One Brazilian study reported a prevalence of 1.3% of secondary headache disorders within primary care practices. 30 This may actually overestimate the prevalence of secondary headache within typical primary care practices, since some of these sites may have also performed emergency care. Emergency care may increase the prevalence of secondary headache disorders to 4%. Table. SNOOP Mnemonic for Secondary Headache Disorders Mnemonic Meaning Examples STEP 2: USE ABBREVIATED CRITERIA TO IDENTIFY MIGRAINE Both single and multiple variable models of abbreviated criteria have sufficient positive predictive value to be useful within primary care for the diagnosis of migraine headache. The single-variable models with the highest positive predictive value were nausea/vomiting, photophobia, and moderate/severe disability. The multivariate models proposed by Lipton et al 23 and Pryse-Phillips et al 25 had positive predictive value similar to the univariate models. A positive response to any of these models increases the likelihood of migraine to >70% in those populations with a prevalence of migraine of >40% (40% to 60% represents a conservative estimate of the prevalence S Systemic sign or symptoms Fever, weight loss, history of malignancy or HIV, meningismus N Neurologic signs or Hemiparesis, hemisensory loss, symptoms diplopia, dysarthria O Onset Worst headache of life, headache that reaches peak intensity within seconds to minutes (eg, thunderclap headache) O Old age New onset headache >40 years of age P Progression of an existing Change in the quality, location, headache disorder or frequency of existing headaches HIV = Human immunodeficiency virus. Advanced Studies in Medicine 205

7 CLINICAL DECISION MAKING of migraine in those with a complaint of headache). The author would contend that a probability of >70% represents a reasonable threshold for institution of migraine-specific therapies. While these models increase the probability of migraine, they should not be considered an absolute gold standard for its diagnosis. The main advantage of models with multiple variables is their high positive and negative predictive value. Generally, single-variable models provide one or the other, but rarely do they provide both together. The exception to that rule is photophobia, which maintains both positive and negative predictive value. The main disadvantage to the multivariate models is the fact that primary care physicians must remember 3 variables at the same time to make a diagnosis. To overcome this obstacle, it may be more reasonable to administer these models as self-administered questionnaires to patients. Also, the current multivariate models must be validated in separate studies to confirm their performance in other than primary care populations. Of the 2 multivariate models, the authors favor use of the ID Migraine questionnaire by Lipton et al, 23 since it was both developed and validated in a primary care population. Figure 4. Migraine-Specific and Nonspecific Treatments* *Migraine-specific therapies have proven efficacy in those patients with a diagnosis of migraine headache, whereas migraine-nonspecific therapies have proven efficacy in patients with a diagnosis of either migraine or tension-type headaches. NSAIDs = nonsteroidal anti-inflammatory drugs. STEP 3: CONSIDER USE OF MIGRAINE-SPECIFIC THERAPIES Once secondary headache disorders have been ruled out, the 2 most common diagnoses are migraine and tension-type headaches. A diagnosis would not be necessary if all therapies could be used interchangeably for migraine or tension-type headache. Some medications, however, have proven efficacy only in populations with migraine, whereas others are efficacious in those with migraine or tension-type headache. Migraine-specific therapies are preventive and abortive treatments that have proven efficacy only in populations with a diagnosis of migraine; migraine-nonspecific therapies have proven efficacy in populations with either migraine or tension-type headaches. For example, tricyclic antidepressants are an effective preventive therapy for patients with either migraine or tension-type headaches, whereas beta blockers, calcium-channel blockers, and anticonvulsants have proven efficacy only for patients with migraine. 31,32 Triptans abort attacks of both migraine and tension-type headaches when they coexist in the same patient 33 but are not effective for attacks of tension-type headaches when they occur in patients without a history of migraine. 34 Therefore, even in the former case, a prior diagnosis of migraine headache would be necessary in order to prescribe the triptans. Examples of other migraine-specific and nonspecific therapies are listed in Figure 4. It should not be assumed that migraine-specific medications are always superior to nonspecific therapies, as there is tremendous variability in response to medications. A diagnosis of migraine headache, however, drastically increases the armamentarium of medications available for preventive or abortive therapy. The impact of migraine headache on the patient should influence the decision to prescribe migrainespecific abortive treatments. The Disability in Strategies for Care study 35 compared 2 treatment strategies in the abortive treatment of migraine. The stratified care approach involves prescribing more effective and often more expensive migraine-specific therapies (eg, triptans) for the most disabled migraineurs and less effective, migraine-nonspecific medications (eg, nonsteroidal anti-inflammatory drugs) for the less disabled migraineurs. The step care approach uses the lower end therapies to initiate treatment for all patients regardless of their disability and ramps up to the higher end therapies only if needed. The disability level was assessed using the Migraine Disability Assessment (MIDAS) questionnaire, which designates the disability levels caused by 206 Vol. 4, No. 4 April 2004

8 MIGRAINE HEADACHE migraine as grades 1 to 4 (1 = minimal or infrequent disability, 2 = mild or infrequent disability, 3 = moderate disability, and 4 = severe disability). Those randomized to the stratified care group first received a triptan for 6 consecutive migraine headaches if their initial disability rating was moderate or severe (MIDAS 3 or 4), and they first received aspirin and metoclopramide if the rating was mild (MIDAS 2). Those in the step care group received aspirin and metoclopramide first for all migraines and took the triptan only if the headaches were not adequately treated 2 hours into the attack. The stratified care group had greater pain relief at 2 hours averaged over the 6 attacks as compared to the step care group (53% vs 37%, respectively); the difference in pain relief was statistically significant (P <.001). Therefore, for abortive treatment, outcomes may be improved through use of a stratified care approach. One might entertain the use of migraine-specific medications for those who have more severe and disabling migraines or who have not found the step care approach beneficial. CONCLUSION Migraine headache should be considered the leading diagnosis in those presenting with episodic headache to their primary care physician. The most important factor leading to misdiagnosis is that 2 headache disorders often coexist in the same patient. A physician can differentiate the headache type by asking patients to describe their more severe headaches. Migraine should be suspected in patients with any 1 of the following characteristics: (1) nausea or vomiting, (2) photophobia, or (3) moderate to severe disability. Three-item questionnaires such as the ID Migraine and the Canadian model have very good positive and negative predictive value in the diagnosis of migraine. They may be most useful when selfadministered by the patient. Clinicians should follow a logical sequence of steps when diagnosing and treating the patient with migraine headache: (1) rule out secondary headache disorders; (2) use abbreviated migraine criteria to identify migraine headache; and (3) consider migraine-specific therapies if the patient has moderate to severe disability with his/her headaches or nonspecific therapies have failed to control symptoms. ACKNOWLEDGMENTS The author would like to thank Gregory Rouan, MD, for his editorial assistance and Fred Taylor, MD for his help in the development of this manuscript. REFERENCES 1. Benson V. Marano MA. Current estimates from the National Health Interview Survey, Vital Health Statistics, Series 10, No Hyattsville, Md: US Dept of Health and Human Services; 1998; Lipton RB, Stewart WF, Diamond S, Diamond ML, Reed M. Prevalence and burden of migraine in the United States: data from the American Migraine Study II. Headache. 2001;41: Menken M, Munsat TL, Toole JF. 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9 CLINICAL DECISION MAKING 20. Rasmussen BK, Jensen R, Olesen J. Questionnaire versus clinical interview in the diagnosis of headache. Headache. 1991;31: Martin V, Penzien D, Andrew M, Houle T. The predictive value of Abbreviated Diagnostic Criteria for migraine headache. Headache. 2002;42(5): Rasmussen BK, Jensen R, Olesen J. A population-based analysis of the diagnostic criteria of the International Headache Society. Cephalalgia. 1991;11: Lipton RB, Dodick D, Sadovsky R, et al. A self-administered screener for migraine in primary care: the ID Migraine(TM) validation study. Neurology. 2003;61: Rothrock J, Patel M, Lyden P, Jackson C. Demographic and clinical characteristics of patients with episodic migraine versus chronic daily headache. Cephalalgia. 1996;16:44-49; discussion Pryse-Phillips W, Aube M, Gawel M, Nelson R, Purdy A, Wilson K. A headache diagnosis project. Headache. 2002; 42: Solomon S, Lipton RB. Criteria for the diagnosis of migraine in clinical practice. Headache. 1991;31: Lipton RB, Stewart WF, Celentano DD, Reed ML. Undiagnosed migraine headaches: a comparison of symptom-based and reported physician diagnosis. Arch Intern Med. 1992;152: Maizels M, Burchette R. Rapid and sensitive paradigm for screening patients with headache in primary care settings. Headache. 2003;43: Ware J, Bayliss M, Kosinski M, et al. Accuracy of the headache impact test for migraine case finding [abstract]. Cephalalgia. 2000;20: Bigal ME, Bordini CA, Speciali JG. Etiology and distribution of headaches in two Brazilian primary care units. Headache. 2000;40: Silberstein, SB. Practice parameter: evidence-based guidelines for migraine headache (an evidence-based review): report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology. 2000;55: Erratum in: Neurology. 2000;56: Holroyd KA, O Donnell FJ, Stensland M, Lipchik GL, Cordingley GE, Carlson BW. Management of chronic tension-type headache with tricyclic antidepressant medication, stress management therapy, and their combination: a randomized controlled trial. JAMA. 2001;285: Lipton RB, Stewart WF, Cady R, et al Wolfe Award. Sumatriptan for the range of headaches in migraine sufferers: results of the Spectrum Study. Headache 2000;40: Brennum J, Brink T, Schriver L, et al. Sumatriptan has no clinically relevant effect in the treatment of episodic tension-type headache. Eur J Neurol. 1996;3: Lipton RB, Stewart WF, Stone AM, Lainez MJ, Sawyer JP. Disability in Strategies of Care Study group. Stratified care vs step care strategies for migraine: the Disability in Strategies for Care (DISC) Study: a randomized trial. JAMA. 2000;284: See Tables A and B on the next page. Appendix Operating Characteristics of Diagnostic Tests The following section includes sample calculations for the operating characteristics of diagnostic tests: For example, if the sensitivity of a test is 81% and the specificity is 75% then the positive likelihood ratio (LR) is 3.2 (.81/[1-.75]=3.2) and the negative LR is 0.25 ([1-0.81]/0.75= 0.25). Positive and negative LRs are multiplied by the pretest odds of disease to determine the posttest odds of disease. If the pretest odds are 1:1 (equivalent to a pretest probability of 50%; [0.5/(1-0.5)=1] and the positive LR is 3.2 then the posttest odds are 3.2 (1 x 3.2=3.2). A posttest odds of 3.2:1 is equivalent to a posttest probability of 76% (3.2/(3.2+1)=0.76). Therefore, a positive response on this test increases the probability of the disease to 76% and a negative response decreases the likelihood of disease to 20%. In the case of migraine, the pretest probability is equivalent to the prevalence of migraine headache in patients presenting to their primary care physician with a chief complaint of headache. A conservative estimate of its prevalence in those patient populations is 40%-60%. Therefore, using pretest probabilities in this range a test must have a positive LR >3 and a negative LR < 0.3 to have posttest probabilities of >70% and <30%, respectively. 208 Vol. 4, No. 4 April 2004

10 MIGRAINE HEADACHE Table A. Operating Characteristics of Diagnostic Tests* Sensitivity Specificity TP/(TP + FN) TN/(TN +FP) Positive Likelihood Ratio Sensitivity/(1-Specificity) Negative Likelihood Ratio (1-Sensitivity)/Specificity Post Test Odds Post Test Odds= Pretest Odds x LR** Odds Odds= probability/(1-probablity) Probability Probability= Odds of disease/(odds of disease +1) *TP= true positives, TN= true negatives, FP= false positives, FN= false negatives, LR= Likelihood Ratio Table B. Operating Characteristics of Models with a Single Variable* International Headache Positive Likelihood Negative Likelihood Society Criteria Ratio Ratio Nausea Vomiting Photophobia *When the presenting complaint is headache, and the patient gives an affirmative response to a question about 1 of the symptoms listed above, the posttest probability is >70% that a diagnosis of migraine headache will be correct. A negative response to the photophobia question confers a posttest probability of <30% that a diagnosis of migraine headache will be correct. Represents the range of likelihood ratios from the studies listed below. Data derived from studies by Rasmussen, 23 Rothrock, 21 Martin, 22 and Lipton. 24 Table C. Operating Characteristics of Disability in the Diagnosis of Migraine Headache* Author, Disability Positive Negative Year Measure Likelihood Ratio Likelihood Ratio Lipton How many days did your headaches limit you from working, studying, or doing what you needed to do? (>1 day in last 3 months) Maizels How often do you get episodic severe headache (difficult or unable to continue normal functioning)? Ware HIT-6 Questionnaire Score > > > > *The studies of Lipton 24 and Maizels 27 used questions to identify any degree of disability of headache and consequently those questions had excellent negative predictive value but poor positive predictive value. The HIT-6 questionnaire of Ware 28 demonstrated excellent positive predictive value for the diagnosis of migraine headache as the scores reached moderate to severe levels of disability (scores >50). Advanced Studies in Medicine 209