A B S T R A C T Purpose: We sought to test the effectiveness and application of a system for prioritizing corneal disease patients for corneal transplantation. Methods: All patients wait-listed for corneal transplantation in British Columbia in April 1995 were followed for 10 months to determine whether they received surgery and to assess the application of recently introduced priority criteria. Results: The factors that determined whether a patient had surgery were as follows: having vision in one eye only, being female, having progressive disease, and experiencing pain. The surgeon involved was also a factor. Overall, the priority system did not adequately predict who had surgery and who did not have surgery. Conclusions: The priority system needs to be re-structured to reduce the contribution of months waited and to more adequately take into account patient need. Furthermore, its application by individual surgeons needs to be strengthened. A B R É G É Objectif : Nous avons cherché à tester l efficacité et l application d un système destiné à définir l ordre de priorité des patients en attente d une greffe de cornée. Méthodes : Tous les patients sur la liste d attente pour une greffe de cornée, en Colombie-Britannique, ont été suivis à partir d avril 1995 pendant une période de 10 mois pour déterminer s ils avaient été opérés ou non et pour évaluer l application des critères de priorité récemment mis en vigueur. Résultats : Les facteurs qui déterminaient si un patient devait être opéré étaient les suivants : ne voir que d un oeil, être femme, être atteint d une maladie évolutive, et souffrir. Le chirurgien concerné est aussi apparu comme un facteur. Dans l ensemble, le système de définition de la priorité n a pas réussi à permettre de prévoir adéquatement qui serait opéré et qui ne le serait pas. Conclusions : Le système définissant l ordre de priorité doit être restructuré pour réduire le nombre de mois d attente et mieux prendre en compte les besoins des patients. En outre, son application par les chirurgiens doit être renforcée. Creation of Priority Criteria for Corneal Transplantation and Analysis of Factors Associated with Surgery Following Implementation Paul Courtright, DrPH, 1 Christina I. Poon, MSc, 1 John S.F. Richards, MD, FRCSC, 2 Debbie L. Chow, COMT, CEBT, 3 Glenn Ottenbreit, COMT, CEBT, 3 Simon P. Holland, MD, FRCSC 1 Corneal transplantation, the removal of diseased corneal tissue and replacement with healthy tissue from a deceased donor, is the last option for patients with corneal scars that impede vision. In Canada there are approximately 3,000 corneal transplantations per year. The increasing demand for better visual function, the potential or actual shortage of corneal tissue for transplantation, the high cost of importing tissue, inadequate surgical time, and shrinking health budgets have led to the creation of waiting lists for corneal transplantation in Canada and elsewhere. To date, there has been little work to develop routine criteria for prioritizing patients for this procedure. In Canada, assessment of wait listing and prioritization for surgery has been well developed in the field of cardiac surgery. 1,2 In most cases, priority grading has been in response to the growth of large waiting lists for surgery. Recently, the increasing demand for cataract surgery has led to the creation of a priority system for cataract surgery in New Zealand. 3 Corneal transplantation, like cataract surgery, is an elective procedure in most cases. The priority criteria developed in New Zealand take 1. British Columbia Centre for Epidemiologic & International Ophthalmology, Department of Ophthalmology, University of British Columbia 2. Department of Ophthalmology, University of British Columbia 3. Eye Bank of British Columbia This study was supported in part by the Eye Bank of British Columbia. Correspondence and reprint requests: Dr. Paul Courtright, British Columbia Centre for Epidemiologic & International Ophthalmology, University of British Columbia, St. Paul's Hospital, 1081 Burrard Street, Vancouver, BC V6Z 1Y6 into account both clinical and social factors and have, as a basic aim, to maximize the health benefit from available funds. Hospital waiting lists have been the subject of an annual report from the Fraser Institute. 4 According to the 1996 report the median patient wait for corneal transplantation after appointment with a specialist was highest in the western provinces (52.5 weeks in British Columbia, 44 weeks in Alberta, and 52 weeks each in Saskatchewan and Manitoba). The median reasonable patient wait (as defined by the ophthalmologist) for corneal transplantation is 12 weeks in British Columbia, 9 in Alberta, 20 in Saskatchewan and 8 in Manitoba. These numbers reflect the opinions of ophthalmologists rather than the perceived needs of patients who may require corneal transplantation. The Eye Bank of British Columbia (EBBC) wait list for corneal transplantation in British Columbia grew from 500 in 1991 to over 1,000 in early 1995. Patients who had conditions that required emergency correction (e.g., corneal perforation) were not included on the wait list. Before 1995 patients were prioritized according to the number of months waited, and the wait list was maintained by the surgeon. Factors such as the number of patients on the surgeon's wait list, time waited, the amount of surgical time available, and persistence of the patient influenced the surgeon's decisions to perform surgery. In response to the increasing numbers wait listed, in January 1995 the EBBC established priority criteria based on a number of clinical factors and on months waited, to create an overall priority score 320 REVUE CANADIENNE DE SANTÉ PUBLIQUE VOLUME 88, NO. 5
for patients waiting for a corneal transplant. The criteria (listed in Table I) were proposed by the participating surgeons. As before, patients with conditions requiring emergency surgery were not included on the wait list. The priority criteria were approved by all corneal surgeons prior to their implementation; the primary drive to develop priority criteria was generated by a few surgeons with a high volume of patients. Allocation of corneal tissue to surgeons was not linked to the overall priority score of patients. Instead, individual surgeons were provided a list of their patients, ordered according to the patient priority scores. Although creation of standardized priority criteria is a crucial first step in the provision of services to those with the greatest need it is important to assess the application of a priority scheme and to determine whether the scheme reflects both patient needs and, eventually, improved patient quality of life. There is little information on the application of priority criteria and, in an effort to improve the system whereby patients undergo corneal transplantation according to their need, we sought to determine whether the present priority criteria predicted which patients had surgery. Furthermore, we sought to refine the priority criteria to more accurately reflect patient needs for surgery. METHODS All patients included on the April 1995 EBBC wait list for corneal transplantation (n=882) were potential study subjects. Since the priority criteria went into effect in January 1995 we waited until April to make sure it was well in place before the start of the study. Patients names are placed on the EBBC wait list by individual British Columbia corneal surgeons (n=19). All transplant tissue in British Columbia is managed through the EBBC. In February 1996 (10 months after study initiation and 14 months after the priority scheme was started) all patients from the April 1995 wait list were traced through the EBBC to determine surgical status. Surgical status was defined as one of the following: had surgery, did not have surgery (still on wait list), or did not have TABLE I Priority Listing Scheme for Corneal Transplantation in British Columbia (January, 1995) Priority Items TABLE II Demographic and Clinical Factors Associated with Selection of Patients for Corneal Transplantation (April 1995-February 1996) Parameter Patient Had Patient Still Relative Risk Surgery on Wait List (95% CI) No. (%) No. (%) p value Mean age (SD) 61.9 (19) 57.4 (20) p<0.001 Sex Female 189 (46) 223 (54) 1.0 (reference group) Male 119 (33) 243 (67) 0.72 (0.6-0.9)*** Group Non-minority 232 (42) 323 (58) 1.0 (reference group) Visible minority 70 (34) 138 (66) 0.81 (0.6-1.0)* Clinical diagnosis Bullous keratopathy 70 (54) 59 (46) 1.0 (reference group) Fuch's endothelial dystrophy/other dystrophy 100 (40) 152 (60) 0.73 (0.6-0.9)** Injury 15 (31) 33 (69) 0.58 (0.4-0.9)** Keratoconus 57 (34) 111 (66) 0.63 (0.5-0.8)*** Herpes simplex Keratitis 16 (35) 30 (65) 0.64 (0.4-0.9)* Graft rejection 33 (36) 60 (65) 0.65 (0.5-0.9)** Other 18 (43) 24 (57) 0.79 (0.5-1.2) Vision in eye to be operated Not visually impaired (>20/55) 28 (37) 47 (63) 1.0 (reference group) Visually impaired (20/200-20/55) 113 (39) 179 (61) 1.04 (0.7-1.4) Blind (<20/200) 167 (41) 238 (59) 1.10 (0.8-1.5) Best corrected vision (in better eye ) Not visually impaired 192 (37) 325 (63) 1.0 (reference group) Visually impaired 83 (44) 108 (57) 1.17 (0.9-1.4) Blind (<20/200) 33 (53) 29 (47) 1.43 (1.1-1.9)* Surgeon High volume 210 (34) 407 (66) 1.0 (reference group) Low volume 102 (61) 65 (39) 1.79 (1.5-2.1)*** SD = Standard deviation, CI = Confidence interval. Statistical significance at * p<0.05, ** p<0.01, or *** p<0.001. Visible minority defined as East Asian, South Asian or other; non-minority defined as Caucasian and First Nations. Information missing on other eye in 2 patients. Low volume defined as <50 patients on the wait list; high volume defined as 50 patients on the wait list. surgery (removed from the wait list). Analysis did not include information on the last group, those removed from the list. Because of the large number of corneal surgeons receiving tissue from the EBBC we have grouped them by the size of their wait list. Low volume surgeons (n=15) had fewer than 50 patients on the wait list Allocation of Points Progressive corneal condition Yes = 5 No = 0 Vision in one eye only Yes = 10 No = 0 Legal blindness Yes = 10 No = 0 Good potential result Yes = 5 No = 0 Pain Constant = 10 Intermittent = 5 No = 0 Each month on the wait list 1 point whereas high volume surgeons (n=4) had more than 50 patients on the wait list. Relative risks and 95% confidence intervals were calculated for surgical coverage according to specific baseline characteristics. For continuous variables, Student s t tests were calculated. A non-parametric statistic (Mann-Whitney U test) was calculat- SEPTEMBER OCTOBER 1997 CANADIAN JOURNAL OF PUBLIC HEALTH 321
TABLE III Eye Bank of British Columbia Priority Score Associated with Selection of Patients for Corneal Transplantation (April 1995-February 1996) Priority Item Patient Had Patient Still Relative Risk Surgery on Wait List (95% CI) No. (%) No. (%) p value Progressive disease No 52 (31) 114 (69) 1.0 (reference group) Yes 256 (42) 352 (58) 1.34 (1.1-1.7)* Vision in one eye only No 253 (36) 442 (64) 1.0 (reference group) Yes 55 (70) 24 (30) 1.91 (1.6-2.3)*** Legally blind No 259 (38) 416 (62) 1.0 (reference group) Yes 49 (50) 50 (51) 1.29 (1.0-1.6)* Pain No 219 (37) 373 (63) 1.0 (reference group) Intermittent 68 (45) 82 (55) 1.23 (1.0-1.5) Constant 21 (66) 11 (34) 1.77 (1.4-2.3)** Potential for clear cornea Not good 31 (48) 33 (52) 1.0 (reference group) Good 277 (39) 433 (61) 0.81 (0.6-1.1) Mean number of 15.2 [10.3] 15.8 [11.7] NS months on list [SD] Median [Range] 13 [1-42] 14 [1.56] Mean priority score without months [SD] 13.8 [6.7] 11.1 [5.1] p<0.001 Mean priority score with months included [SD] 29.0 [9.8] 26.8 [12.8] p=0.008 SD = Standard deviation, CI = Confidence interval. Statistical significance at * p<0.05, ** p<0.01, and *** p<0.001; NS = not statistically significant at p<0.05. Variances significantly different at p<0.05, Mann Whitney U test used to test statistical significance. Model #1: Priority grading score ed when the data were not normally distributed. As multiple factors were associated with surgery, a multiple regression TABLE IV Findings from Logistic Regression Model Priority Score Factor Adjusted Odds Ratio p value (95% CI) Progressive disease 1.09 (1.06, 1.14) 0.02 Vision in one eye only 1.14 (1.12, 1.18) <0.001 Legal blindness 1.03 (1.00, 1.05) NS Pain 1.08 (1.05, 1.12) 0.006 Potential clear cornea 1.01 (0.95, 1.07) NS Months 1.00 (0.99, 1.01) NS Model #2: All factors associated (univariate) with surgery. Priority Score Factor Adjusted Odds Ratio p value (95% CI) Progressive disease 1.12 (1.07, 1.17) 0.01 Vision in one eye only 1.17 (1.14, 1.21) <0.001 Pain 1.08 (1.05, 1.12) 0.01 Sex (=female) 1.70 (1.44, 2.01) 0.001 Surgeon (=low volume) 3.41 (2.78, 4.19) <0.001 Age 1.00 (0.99, 1.01) NS Diagnosis (=bullous keratopathy) 1.10 (0.86, 1.41) NS Ethnic group (=non-immigrant) 1.07 (1.00, 1.12) NS Best corrected vision 1.23 (1.00, 1.40) NS NS=not significant, CI=confidence interval. model was constructed to determine the independent contribution of factors to surgical correction. RESULTS Of the 882 patients on the wait list in 1995, 98 patients were removed from the list by the surgeon. Patients removed from the wait list comprised those who died (n=3) or those whom the surgeon no longer considered as an "active" case (n=95). Thus, 784 patients were possible surgical cases. The mean age of these patients was 59.2 years; 47% were males and 53% females. Twenty-eight percent of the patients were from visible minority groups, primarily from South and East Asia. Bilateral blindness (<20/200 in the better eye) was recorded in 62 patients (8%), and blindness in the affected eye was recorded in 405 patients (52%). At the 10-month follow-up, 312 of the patients (40%) on the wait list had had surgery. Univariate analysis of demographic and clinical factors revealed that age, sex, minority status, diagnosis, best-corrected vision, and surgeon predicted which patients had surgery (Table II). Patients who underwent surgery had obtained an overall priority score of 29.0 (median=29, range 9-69) whereas patients who did not have surgery had obtained an overall priority score of 26.8 (median=24, range 6-71). Analysis of the components of the priority score suggested that only two of the six priority criteria, pain and the presence of vision in one eye only, contributed significantly to who received surgery (Table III). Of the other criteria, the potential for a clear cornea and months on wait list did not contribute; legal blindness and progressive disease contributed only slightly. Using multiple logistic regression we constructed two models. The first model included only those criteria in the priority scheme. Findings revealed that pain, vision in one eye only, and progressive disease were the only independent predictors of surgery (Table IV). Including other factors in the model (those demonstrating statistical significance by univariate analysis) demonstrated that surgeon, sex, vision in one eye only, pain and progressive eye disease predicted who received surgery. The fact that surgeon was a strong predictive factor suggested that there was considerable variation in how the priority system was used by individual surgeons (Figures 322 REVUE CANADIENNE DE SANTÉ PUBLIQUE VOLUME 88, NO. 5
1-3). Some surgeons continued to use the number of months waiting as the primary criterion to decide who had surgery, and for one surgeon the only factor associated with surgery was age. The average age of patients having surgery was 81.6 and for patients not having surgery was 55.3 (p<0.001). We assessed the priority system itself to determine the weight of each factor. The number of months that a patient was on the wait list contributed about 58% of the weight of the wait list priority score (Table V). One of the clinical parameters, potential for a good outcome, was reported as favourable in 93% of patients, adding little practical value to the priority score while contributing 16% of the overall weight. DISCUSSION Figure 1. Figure 2. Clinical priority score (first 5 parameters in Table I) of patients who did and did not have surgery by surgeon. Surgeons A-D are high volume surgeons; all low volume surgeons are grouped as E. Differences for surgeons A, B, and E are statistically significant at p<0.01. Months on the wait list for patients who did and did not have surgery. Differences for surgeons A and C are statistically significant at p<0.01. Development of technically acceptable guidelines is often the easiest component of evidence-based medicine. The most difficult challenge is changing physician behaviour. The findings from our study suggest that there is considerable variation among surgeons in the selection of patients for surgery. These results and our evaluation of a patient-derived visual function assessment have led to changes to the priority system, also listed in Table V. Briefly, they include increasing the overall weight of specific clinical factors, in particular pain, vision in one eye only, and best corrected visual acuity. Clinical factors will continue to contribute about 42% of the total score. The contribution of months waiting has been reduced from 58% of the total score to around 22%. Finally, the new priority criteria also include a standardized patientderived visual function assessment. Currently, the EBBC allocates corneal tissue according to the surgical time available to each surgeon, which is often based upon the size of the surgeon's wait list. The possibility of linking allocation of tissue to surgeons on the basis of the priority scores of their patients has not been addressed. Application of the updated priority criteria will require additional education of the surgeons and their staff, and the development of an infrastructure for routine evaluation of its application. The next phase of the project includes further assessment of application of the new priority scheme and whether it leads to improvement in patient quality of life and patient satisfaction with surgery, the true measures of the value of surgery. As demands for accountability increase, measuring the appropriateness of service (through adoption of clinical practice guidelines 5 ) and outcome, in terms of a patient s visual function will become the cornerstone of service delivery. 6 Although this project has led to changes in the priority scheme for corneal transplantation, caution must be used in the extrapolation of our findings. The identification and weighting of clinical and social factors included in the priority criteria will likely change, particularly in response to an assessment of the outcome of surgery. Patient education of the application of the priority criteria has not been undertaken; although priority criteria may help clini- SEPTEMBER OCTOBER 1997 CANADIAN JOURNAL OF PUBLIC HEALTH 323
cians decide who should be treated first, patients also need to understand when to reasonably expect treatment. Further development and evaluation of the EBBC priority criteria for corneal transplantation could assist others within ophthalmology create mechanisms for ensuring that patients with the greatest need receive surgery in a timely fashion. REFERENCES Figure 3. Priority score (clinical score + months on wait list) of patients who did and did not have surgery. Differences for surgeons A, B and E (low volume surgeons) are statistically significant at p<0.01. TABLE V Comparison of 1995 and 1996 (updated) EBBC Priority Grading of Patients Wait-Listed for Corneal Transplantation Parameter 1995 Score 1996 Score % of Total Score System System 1995 1996* Vision in one eye only No = 0 No = 0 3.8% 7.3% Yes = 10 Yes = 25 Legal blindness No = 0 20/50 = 0 4.4% 8.4% Yes = 10 20/60-20/80 = 8 20/100-20/200 = 16 <20/200 = 25 1. Higginson LAJ, Cairns JA, Keon WJ, Smith ER. Rates of cardiac catheterization, coronary angioplasty and open-heart surgery in adults in Canada. CMAJ 1992;146:921-25. 2. Maziak DE, Rao V, Christakis GT, et al. Can patients with left main stenosis wait for coronary artery bypass grafting? Ann Thorac Surg 1996;61:552-57. 3. Hadorn DC, Holmes AC. The New Zealand priority criteria project. Part 1: Overview. BMJ 1997;314:131-34. 4. Ramsay C, Walker M. Waiting Your Turn: Hospital Waiting Lists in Canada 6th edition. Vancouver: The Fraser Institute, 1996. 5. American Academy of Ophthalmology. Corneal Opacification Preferred Practice Pattern. San Francisco: American Academy of Ophthalmology, 1995. 6. Lavis JN, Anderson GM. Appropriateness in health care delivery: Definitions, measurement and policy implications. CMAJ 1996:154:321-28. 7. Steinberg EP, Tielsch JM, Schein OD, et al. The VF-14. An index of functional impairment in patients with cataract. Arch Ophthalmol 1994;112:630-38. Received: April 3, 1997 Accepted: August 11, 1997 Pain No = 0 No = 0 4.9% 16.1% Intermittent = 5 Intermittent = 20 Constant = 10 Constant = 50 Progressive disease No = 0 No = 0 13.5% 10.4% Yes = 5 Yes = 5 Potential for good outcome No = 0 [removed] 15.6% 0 Yes = 5 Months on list 1 for each month 0.5 for each month 58.0% 22.3% Visual function assessment (not included VF score x 5 0 35.5% in priority score) * 1996 value calculated using 1995 waiting list. Visual function (VF) assessment includes 15 items; scoring is similar to the VF-14. 7 324 REVUE CANADIENNE DE SANTÉ PUBLIQUE VOLUME 88, NO. 5