title: Screening for diabetic retinopathy with or without a copayment in a randomized controlled trial: influence of the inverse care law.
abstract: OBJECTIVE
  To examine whether the inverse care law operates in a screening program for diabetic retinopathy (DR) based on fee for service in Hong Kong.
  
  
  METHODS
  Randomized controlled trial.
  
  
  METHODS
  All those with type 1 or 2 diabetes from 2 clinics were recruited.
  
  
  METHODS
  Diabetic retinopathy screening with a small copayment versus free access in a publicly funded family medicine service.
  
  
  METHODS
  Uptake of screening and severity of DR detected. Association between these outcome variables and independent variables were determined using multivariate logistic regression models and reported as odds ratios (ORs).
  
  
  RESULTS
  After randomization, 1387 subjects in the free group and 1379 subjects in the pay group were eligible for screening, and 94.9% (1316/1387) and 92.6% (1277/1379), respectively, agreed to participate in the study. The offer of screening was accepted by 94.8% (1247/1316) in the free group and 91.2% (1164/1277) in the pay group, and the final uptake ratios were 88.5% (1165/1316) and 82.4% (1052/1277), respectively (Pearson chi = 19.74, P<0.001). Being in the pay group was associated with a lower uptake of screening than being in the free group (OR, 0.59; confidence interval [CI], 0.47-0.74) and a lower detection rate of DR (OR, 0.73; CI, 0.60-0.90) after adjustment for potential confounding factors. Subjects with higher socioeconomic status were more likely to attend screening and had a lower prevalence of DR detected.
  
  
  CONCLUSIONS
  The inverse care law seems to operate in a preventive intervention when a relatively small copayment is applied. There is a case for making effective preventive services free of charge.
  
  
  BACKGROUND
  The author(s) have no proprietary or commercial interest in any materials discussed in this article.
authors.affiliation: School of Public Health, The University of Hong Kong, Hong Kong.
authors.forename: Jin Xiao
authors.initials: JX
authors.lastname: Lian
authors.forename: Sarah M
authors.initials: SM
authors.lastname: McGhee
authors.forename: Rita A
authors.initials: RA
authors.lastname: Gangwani
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Hedley
authors.forename: Cindy Lo Kuen
authors.initials: CL
authors.lastname: Lam
authors.forename: Maurice Keng Hung
authors.initials: MK
authors.lastname: Yap
authors.forename: Wico W
authors.initials: WW
authors.lastname: Lai
authors.forename: Daniel Wai Sing
authors.initials: DW
authors.lastname: Chu
authors.forename: David S H
authors.initials: DS
authors.lastname: Wong
mesh_terms: D001786:Blood Glucose / Q000378:metabolism; D001794:Blood Pressure; D003669:Deductibles and Coinsurance; D003922:Diabetes Mellitus, Type 1 / Q000150:complications; D003924:Diabetes Mellitus, Type 2 / Q000150:complications; D003930:Diabetic Retinopathy / Q000175:diagnosis*; D005260:Female; D006442:Glycated Hemoglobin / Q000378:metabolism; D006297:Health Services Accessibility; D006779:Hospitals, Public; D006801:Humans; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D010342:Patient Acceptance of Health Care; D010821:Physicians, Family; D011314:Preventive Health Services; D012720:Severity of Illness Index; D012923:Social Class; D017664:Uncompensated Care; D014792:Visual Acuity / Q000502:physiology
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human