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1 Int J Biol Med Res. 2011; 2(2): Int J Biol Med Res Volume 2, Issue 2, April 2011 BioMedSiDiret Publiations Contents lists available at BioMedSiDiret Publiations International Journal of Biologial & Medial Researh Journal homepage: International Journal of BIOLOGICAL AND MEDICAL RESEARCH Original artile Using Glyated Hemoglobin HbA1 for diagnosis of Diabetes mellitus: An Indian perspetive. a b* Rajni Dawar Mahajan, Bhawesh Mishra * Both the Authors have ontributed equally to the work and preparation of manusript. a Department of Biohemistry,Lady Hardinge Medial College & Assoiated SSK Hospital, Shaheed Bhagat Singh Marg, Opp. Shivaji Stadium. New Delhi b Department of Biohemistry,Lady Hardinge Medial College & Assoiated SSK Hospital, Shaheed Bhagat Singh Marg, Opp. Shivaji Stadium. New Delhi A R T I C L E I N F O A B S T R A C T Keywords: Glyated Hemoglobin Diabetes Mellitus Average Plasma Gluose Indian Healthare. Glyated Hemoglobin (HbA1) gives an estimate of long-term average glyemi status. It is used routinely to assess glyemi ontrol in diabetis to attain treatment goals and prevent long term ompliations. Its reommendation for diagnosis of diabetes mellitus has evoked mixed response worldwide. We reviewed a number of published artiles to analyze the pros and ons of using HbA1 for diagnosis of Diabetes mellitus in India. We observed that though HbA1 has some indisputable advantages over fasting plasma gluose estimation for diagnosing diabetes mellitus, a number of biohemial, linial and eonomial fators limit its use as single diagnosti agent. Diagnosti methods and laboratories are insuffiiently standardized for HbA1 in India. The liniian must onsider the overall patient profile in addition to a number of loal variations and disorders espeially hemoglobinopathies /anemias before aepting an abnormal HbA1 value. Supportive or repeat tests may be required leading to inrease in ost and delay in diagnosis. In the present Indian senario, espeially the fragmented unorganized health are setor in suburban areas, HbA1 annot be aepted as a sole and independent test to diagnose diabetes mellitus. Copyright 2011 BioMedSiDiret Publiations IJBMR -ISSN: All rights reserved. 1. Introdution Glyated hemoglobin (GHb) is formed by a posttranslational, non-enzymati, substrate-onentration dependent irreversible proess of ombination of aldehyde group of gluose and other hexoses with the amino-terminal valine of the β -hain of hemoglobin [1]. Sine the time it was first desribed, its importane and utility for prognosis, monitoring and diagnosis of diabetes mellitus has been a matter of researh and debate. This artile tries to analyze the pros and ons of using HbA1 as a diagnosti marker for diagnosis of diabetes mellitus in the Indian health are system. In 1958 Allen et. Al [2] published a paper desribing the heterogeneity of haemoglobin A. The frations that eluted at more * Corresponding Author : Dr. Bhawesh Mishra Senior Resident, Department of Biohemistry Lady Hardinge Medial College & Assoiated SSK Hospital, Shaheed Bhagat Singh Marg Opp. Shivaji Stadium.Connaught Plae, New Delhi drbhawesh@gmail.om Copyright 2011 BioMedSiDiret Publiations. All rights reserved. aidi ph on the anion exhanger arboxy methylellulose and migrated more rapidly on eletrophoresis were alled minor haemoglobins or fast haemoglobins. They ould be sub frationated into the speies A(1a), A(1b), A(1), A(1d). The signifiane of these sub-frations was then unlear and often interpreted as artefats or insignifiant. This radially hanged in 1968 when Samuel Rahbar reported on a survey of 1,200 hospital patients that 2 diabeti patients in this group had a fast-moving haemoglobin on starh gel eletrophoresis [3]. A further 47 diabeti subjets inluding 11 hildren with severe diabetes mellitus also had this haemoglobin fration. Later this fast haemoglobin was identified as Allen's HbA1 and the harge differene loalised to the β hain [4]. Homquist et. al. [5] had published on the β hain N terminally bloking group of HbA1 but the definitive struture was eluidated by Bunn et. al. [6] The use of hemoglobin A1 for monitoring the degree of ontrol of gluose metabolism in diabeti patients was proposed in 1976 by Anthony Cerami, Ronald Koenig and o-workers [7].

2 Rajni Dawar Mahajan & Bhawesh Mishra / Int J Biol Med Res. 2011; 2(2): The Prognosti role of HbA1 is well established and aepted. In the normal 120-day lifespan of the red blood ell, gluose moleules reat with hemoglobin, forming glyated hemoglobin. Gluose forms an aldimine linkage with NH2- of valine in the β- hain, undergoing an Amadori rearrangement to form the more stable ketoamine linkage. Glyated hemoglobin has been used primarily to as a marker to identify the average plasma gluose onentration over prolonged periods of time. As the average amount of plasma gluose inreases, the fration of glyated hemoglobin inreases in a preditable way. In diabetes mellitus, higher amounts of glyated hemoglobin, indiating poorer ontrol of blood gluose levels, have been assoiated with ardiovasular disease, nephropathy, and retinopathy. Traditionally, HbA1 has been thought to represent average glyemia over the past 12 to 16 weeks [8]. In fat, glyation of hemoglobin ours over the entire 120-day life span of the red blood ell [9] but within these 120 days reent glyemia has the largest influene on the HbA1 value [10]. Kineti studies have revealed that glyemia in the reent past influenes the GHb values more than the remote past [11]. Thus, mean blood gluose of past 1 month, 2 months and 3 months ontributes 50%, 40% and 10% respetively to the final result. By mathematial modelling the t1/2 of HbA1 is estimated to be 35.2 days [12]. This means that half of glyation seen during estimation has ourred in the previous 35.2 days. The advantage that HbA1 an give as an assessment of average plasma gluose an also be pereived as a drawbak beause it does not give an indiation of the stability of glyemi ontrol. Thus, in theory, one patient with wildly flutuating gluose onentrations ould have the same HbA1 value as one whose gluose varies little throughout the day. The International Diabetes Federation and Amerian College of Endorinology reommend HbA1 values below 6.5%, while Amerian Diabetes Assoiation reommends that the HbA1 be below 7.0% for most patients.[12].pratitioners must onsider an individual patient's health, his/her risk of hypoglyemia, and his/her speifi health risks when setting a target A1C level. Patients at high risk of mirovasular ompliations may gain further benefits from reduing A1C below 7%. Beause patients are responsible for averting or responding to their own hypoglyemi episodes, the patient's input and the dotor's assessment of the patient's self-are skills are also important. The approximate mapping between HbA1 values and eag (estimated average gluose) measurements is given by the following equation:[13] eag(mg/dl) = 28.7 A1C 46.7 eag(mmol/l) = 1.59 A1C 2.59 The Amerian Diabetes Assoiation guidelines are similar to others in advising that the glyosylated hemoglobin test be performed at least two times a year in patients with diabetes that are meeting treatment goals (and that have stable glyemi ontrol) and quarterly in patients with diabetes whose therapy has hanged or that are not meeting glyemi goals[14] DIAGNOSIS OF DIABETES MELLITUS: Historially, the measurement of gluose has been the means of diagnosing diabetes. Type 1 diabetes has a suffiiently harateristi linial onset, with relatively aute, extreme elevations in gluose onentrations aompanied by symptoms, suh that speifi blood gluose ut points are not required for diagnosis in most linial settings. On the other hand, type 2 diabetes has a more gradual onset, with slowly rising gluose levels over time, and its diagnosis has required speified gluose values to distinguish pathologi gluose onentrations from the distribution of gluose onentrations in the non-diabeti population. When seleting the threshold gluose values, the National Diabetes Data Group (NDDG) aknowledged that there is no lear division between diabetis and nondiabetis in the FPG onentration or their response to an oral gluose load, and onsequently, an arbitrary deision has been made as to what level justifies the diagnosis of diabetes whih has been used for two deades [15]. The diagnosis of diabetes was made when 1) lassi symptoms were present; 2) the venous FPG was >140 mg/dl (>7.8 mmol/ l); or 3) after a 75-g gluose load, the venous 2HPG and levels from an earlier sample before 2 h were >200 mg/dl (>11.1 mmol/l). In 1997, the Expert Committee on the Diagnosis and Classifiation of Diabetes Mellitus [16] re examined the basis for diagnosing Diabetes. In omparing the relationship between FPG and 2HPG values and retinopathy, it was apparent that the previous FPG ut point of 140 mg/dl (7.8mmol/l) was substantially above the gluose level at whih the prevalene of retinopathy began to inrease. As a result, the ommittee reommended that the FPG ut point be lowered to >126 mg/dl (7.0 mmol/l) so that this ut point would represent a degree of hyperglyemia that was similar to the 2HPG value and diagnosis with either measure would result in a similar prevalene of diabetes in the population. The 1997 report also reommended that the FPG level, rather than the 2HPG, be the preferred test to diagnose diabetes beause it was more onvenient for patients and less ostly and time onsuming and the repeat-test reproduibility was superior [16] HBA1C FOR DIAGNOSIS OF DM: Chroni hyperglyemia suffiient to ause diabetes-speifi ompliations is the hallmark of diabetes. Common sense would ditate that laboratory measures that apture long-term glyemi exposure should provide a better marker for the presene and severity of the disease than single measures of gluose onentration. Studies onsistently demonstrated a strong orrelation between retinopathy and A1C (17 19) but a less onsistent relationship with fasting gluose levels [20]. The orrelation between A1C levels and ompliations has also been shown in the setting of ontrolled linial trials in type 1 [21] and type 2 [22] diabetes, and these findings been used to establish the widely aepted A1C treatment goals for diabetes are [23]. Large volume of data from diverse populations has now established an A1C level assoiated with an inrease in the prevalene of moderate retinopathy and provides strong justifiation for assigning an A1C ut point of >6.5% for the diagnosis of diabetes This ut point should not be onstrued as an absolute dividing line between normal glyemia and diabetes; however, the A1C level of 6.5% is suffiiently sensitive and speifi to identify individuals who are at risk for developing retinopathy and who should be diagnosed as diabeti. The A1C level is said to be least as preditive as the urrent FPG and 2HPG values. In seleting a diagnosti A1C level >6.5%, the International Expert Committee balaned the stigma and osts of mistakenly identifying individuals as diabeti against the minimal linial onsequenes of delaying the diagnosis in someone with an A1C level >6.5%. An International Expert Committee, after an extensive review of both established and emerging epidemiologial evidene, reommended the use of the A1C test to diagnose diabetes,with a threshold of >6.5%, and ADA affirms this deision. The diagnosti A1C ut point of 6.5% is assoiated with an infletion point for

3 510 Rajni Dawar Mahajan & Bhawesh Mishra / Int J Biol Med Res. 2011; 2(2): retinopathy prevalene, as are the diagnosti thresholds for FPG and 2-h PG. The diagnosti test should be performed using a method that is ertified by the National Glyohemoglobin Standardization Program (NGSP) and standardized or traeable to the Diabetes Control and Compliations Trial (DCCT) referene assay. Point-of-are A1C assays are not suffiiently aurate at this time to use for diagnosti purposes. ADA 2010 Criteria for the diagnosis of diabetes: [24] 1. A1C >6.5%. The test should be performed in a laboratory using a method that is NGSP ertified and standardized to the DCCT assay.* OR 2. FPG >126 mg/dl (7.0 mmol/l). Fasting is defined as no alori intake for at least 8 h.* OR 3. 2-h plasma gluose >200 mg/dl (11.1 mmol/l) during an OGTT. The test should be performed as desribed by the World Health Organization, using a gluose load ontaining the equivalent of 75 g anhydrous gluose dissolved in water.*or 4. In a patient with lassi symptoms of hyperglyemia or hyperglyemi risis, a random plasma gluose >200 mg/dl (11.1 mmol/l). *In the absene of unequivoal hyperglyemia, riteria 1 3 should be onfirmed by repeat testing. Advantages of Hb A1 as reommended means of diagnosing Diabetes After the ADA reommended HbA1C for diagnosis of Diabetes in 2010, it is gradually being aepted for the same worldwide. With advanes in instrumentation and standardization, the auray and preision of A1C assays at least math those of gluose assays. The measurement of gluose itself is less aurate and preise than most liniians realize [25]. There are also potential pre-analyti errors owing to sample handling and the well-reognized lability of gluose in the olletion tube at room temperature [26, 27]. Even when whole blood samples are olleted in sodium fluoride to inhibit in vitro glyolysis, storage at room temperature for as little as 1 to 4 h before analysis may result in dereases in gluose levels by 3 10 mg/dl in non diabeti individuals [26,27,28,29]. By ontrast, A1C values are relatively stable after olletion [30], and the reent introdution of a new referene method to alibrate all A1C assay instruments should further improve A1C assay standardization in most of the world [31,32,33]. The variability of A1C values is also onsiderably less than that of FPG levels, with day-to-day within-person variane of <2% for A1C but 12 15% for FPG [34,35,36]. The onveniene for the patient and ease of sample olletion for A1C testing (whih an be obtained at any time, requires no patient preparation, and is relatively stable at room temperature) ompared with that of FPG testing (whih requires a timed sample after at least an 8-h fast and whih is unstable at room temperature) support using the A1C assay to diagnose diabetes. Compared with the measurement of gluose, the A1C assay is at least as good at defining the level of hyperglyemia at whih retinopathy prevalene inreases; has appreiably superior tehnial attributes, inluding less preanalyti instability and less biologi variability; and is more linially onvenient. A1C is a more stable biologial index than FPG, as would be expeted with a measure of hroni glyemia levels ompared with gluose onentrations that are known to flutuate within and between days. In short it provides a better index of overall glyemi exposure and risk for long-term ompliations, with less biologi variability, less preanalyti instability with no need for fasting or timed samples and and is relatively unaffeted by aute (e.g., stress or illness related) perturbations in gluose levels Limitations of HbA1 as reommended means of diagnosing Diabetes in India: The most important limitation in India is the ost of providing the assay for its routine use. Seond, any ondition that hanges red ell turnover, suh as haemolyti anemia, hroni malaria, major blood loss, gluose-6-phosphate dehydrogenase defiieny, sikle ell anemia or blood transfusions, will lead to spurious A1C results. These onditions inluding the thlassaemias are highly prevalent in ertain parts of India. Besides, Hereditary persistene of fetal Hb, renal insuffiieny,malignany, iron defiieny anemia, vitamin B 12 and folate defiieny, splenetomy also show inreased values [37,38,39]. Some studies have shown that aloholism, lead poisoning, opiate addition, exessive use of saliylate and pregnany an lead to falsely elevated HbA1. Age and regional differenes do exist in values of HbA1 whih have not been studied widely in India. We do not have suffiient data on whether Indians are high glyaters or low glyaters [40]. HbA1 assay results annot be trusted In ertain rare linial settings, suh as rapidly evolving type 1 diabetes, where the A1C level will not have had time to ath up with the aute elevations in gluose levels [29]. HbA1 test are performed using different methods like High performane liquid hromatography, affinity hromatography, ation exhange hromatography, isoeletri foussing, radioimmunoassay, spetrophotometri assay, eletrophoresis and eletrospray mass spetrometry. Tests to diagnose diabetes should be performed using linial laboratory equipment using a method that is NGSP ertified and standardized to the DCCT assay [41]. Point-of-are instruments have not yet been shown to be suffiiently aurate or preise for diagnosing diabetes. Looking at the enormous variation in the health are system in India, labs and methods used for estimation appear to be far from standardized. With dearth of aredited labs and limited resoures, the routine use of HbA1 is questionable. It would not be pratial to have HPLC as the only method for HbA1 assessment to be used for diagnosti puposes. Also aording to Ranho Bernardo study, the HbA1C ut point of 6.5% had a sensitivity/speifiity of 44/79%. In their ohort of older adults, the suggested HbA1C ut point of 6.5% had relatively low sensitivity and speifiity for type 2 diabetes diagnosis in all age-groups and in both sexes. They onluded that the limited sensitivity of the A1C test may result in delayed diagnosis of type 2 diabetes, while the strit use of ADA riteria may fail to identify a high proportion of individuals with diabetes by HbA1C 6.5% or retinopathy [42]. Also in another study by Cavagnolli et al HbA1 > 6.5% (48 mmol/mol) showed limited sensitivity to diabetes diagnosis, although with high speifiity. The results suggest that this ut-off point would not be enough to diagnose diabetes. They onluded that Its use as the sole diabetes diagnosti test should be interpreted with aution to assure the orret lassifiation of diabeti individuals [43].The deision about whih test to use to assess a speifi patient for diabetes should be at the disretion of the health are professional, taking into aount the availability and pratiality of testing an individual patient or groups of patients. As with most diagnosti tests, a test result diagnosti of diabetes should be repeated to rule out laboratory error, unless the diagnosis is lear on linial grounds, suh as a patient with lassi symptoms of hyperglyemia or hyperglyemi risis. It is preferable that the same test be repeated for onfirmation, sine there will be a greater likelihood of onurrene in this ase. In ase of non onfirmation by repeat testing the healthare professional should opt to follow the patient losely and repeat the testing in 3 6 months. Cliniians should ontinue to use the

4 Rajni Dawar Mahajan & Bhawesh Mishra / Int J Biol Med Res. 2011; 2(2): previously reommended approahes to diagnose diabetes based on gluose measurements. The deision to hange to A1C assays as the means of diagnosing diabetes should take into aount the performane of loal A1C assays and the loal prevalene of onditions that may interfere with the assay. Cliniians must be aware of these onditions, partiularly in populations in whih they are more prevalent. If A1C testing is not possible owing to patient fators that prelude its interpretation (e.g., hemoglobinopathy or abnormal erythroyte turnover) or to unavailability of the assay, previously reommended diagnosti measures (e.g., FPG and 2HPG) and riteria should be used. Mixing different methods to diagnose diabetes should be avoided. The diagnosis of diabetes during pregnany, when hanges in red ell turnover make the A1C assay problemati, ontinues to require gluose measurements. The risk for diabetes based on levels of glyemia is a ontinuum. Therefore; there is no lower glyemi threshold at whih risk learly begins. Those with A1C levels below the threshold for diabetes but > 6.0% should reeive demonstrably effetive preventive interventions. Those with A1C below this range may still be at risk and, depending on the presene of other diabetes risk fators, may also benefit from prevention efforts. The A1C level at whih population-based prevention servies begin should be based on the nature of the intervention, the resoures available, and the size of the affeted population. Conlusion: The major fration of the healthare system in India is a fragmented and unorganized private setor, ranging from orporate hospitals to small linis and private pratitioners [44]. Very few laboratories performing the tests have been standardized [45]. After the ADA 2010 reommendation, there has been a gradual inrease in aeptane of HbA1 as a diagnosti test for diabetes mellitus. But the liniians presribing and interpreting the tests results are likely to miss the numerous limitations, preautions and variations of using HbA1 for diagnosis of diabetes mellitus. Simply speaking every single HbA1 report must be orrelated with the method and lab used. Any disorder of red blood ells or haemoglobin must be exluded and all loal interfering fators disussed above must be taken into aount. Besides a repeat HbA1 testing or plasma gluose estimation is usually reommended before abnormal values an be aepted. All this involves an inreased ost and delay in diagnosis. This might not be a limitation in large organized and standardized ity hospitals. But in the present Indian senario Glyated haemoglobin, HbA1 annot be aepted as a sole and independent test to diagnose diabetes mellitus. Referenes: 1. H. B. Chandalia, P. R. Krishnaswamy. Glyated Haemoglobin. Current Siene,2002; 83 (12): Allen DW, Shroeder WA, Balog J. 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