title: A comparison of disease-specific medical expenditures in Japan using the principal diagnosis method and the proportional distribution method.
abstract: BACKGROUND
  There are technical limitations to handling all the information mentioned in health insurance claims (HICs) in Japan. Therefore, conventional methods for estimating disease-specific medical expenditures assume that all medical care expenditures in a given HIC are spent on only one principal diagnosis even when the HIC contains multiple diagnoses.
  
  
  OBJECTIVE
  To estimate the disease-specific medical expenditures that consider all diagnosis on a given HIC.
  
  
  METHODS
  Data were obtained from 169 622 outpatient HICs in May 2006 from health insurance provided by the employer. We compared the estimated disease-specific medical expenditures of the conventional method with a proportional distribution method (PDM), which considers all diagnoses on the HICs.
  
  
  RESULTS
  For diabetes mellitus and other diseases of the digestive system, the proportion of principal diagnoses among total diagnoses was 52.4% (4849/9251) and 19.6% (2614/13331), respectively. In addition, the ratio of the estimated disease-specific medical expenditures between the conventional method and the PDM method was 1.49 for diabetes mellitus and 0.64 for other diseases of the digestive system. The estimation of disease-specific medical expenditures using the conventional method may therefore have overestimated the expenditures on the disease category typically selected as the principal diagnosis and underestimated the expenditures on the disease category less likely to be selected as the principal diagnosis.
  
  
  CONCLUSIONS
  The conventional method for estimation of disease-specific medical expenditures should be improved by utilizing all the diagnoses information on HICs.
authors.affiliation: Department of Hygiene and Preventive Medicine, School of Medicine, Fukuoka University, Jonan-ku, Fukuoka, Japan. taniyan@cis.fukuoka-u.ac.jp
authors.forename: Shinichi
authors.initials: S
authors.lastname: Tanihara
authors.forename: Etsuji
authors.initials: E
authors.lastname: Okamoto
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Une
mesh_terms: D000328:Adult; D005260:Female; D005102:Health Expenditures / Q000706:statistics & numerical data*; D006801:Humans; D007344:Insurance Claim Reporting; D007345:Insurance Claim Review; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009313:National Health Programs / Q000191:economics*; D012141:Respiratory Tract Infections / Q000191:economics / Q000453:epidemiology; D055815:Young Adult