title: Cost-of-Illness Studies: An Updated Review of Current Methods.
abstract: BACKGROUND
  Cost-of-illness (COI) studies provide policy-relevant information for cross-country, longitudinal, and other cost comparisons. Prior studies have called for standardization in COI methods. We investigated trends, identified factors associated with variation in COI estimation methods, and characterized reporting of heterogeneity in COI estimates.
  
  
  METHODS
  The review of COI studies was implemented following (i) a structured search of PubMed, SCOPUS and EMBASE; (ii) a review of abstracts; (iii) a full-text review; and (iv) classification of articles according to six COI estimation methods: Sum_All Medical, Sum_Diagnosis Specific, Matched, Regression, Other_Total and Other_Incremental. Descriptive and multivariable regression analyses were conducted.
  
  
  RESULTS
  Of the 993 studies included in the full-text review, 186 (18.7 %) were Sum_All Medical, 458 (46.1 %) were Sum_Diagnosis Specific, 96 (9.7 %) were Matched, 97 (9.8 %) were Regression, 70 (7.1 %) were Other_Incremental, and 68 (6.9 %) were Other_Total. Compared with the early period, publications in the middle and late period were associated with lower odds of using Sum_All Medical compared with Sum_Diagnosis Specific (adjusted odds ratio [AOR]middle 0.14; 95 % CI 0.07-0.28; AORlate 0.44; 95 % CI 0.29-0.67). Overall, 640 articles (64 %) reported COI estimates across patient groups defined by patient-level factors, while 247 articles (25 %) reported COI estimates across patient groups defined by non-patient-level factors.
  
  
  CONCLUSIONS
  The disease-specific total costing method (Sum_Diagnosis Specific) was most commonly used and its use increased over the time period covered by this review. The investigation of subgroup heterogeneity in COI estimates represents an area for future research.
authors.affiliation: Department of Pharmaceutical Health Services Research, School of Pharmacy, University of Maryland, 220 Arch Street, Baltimore, MD, 21201, USA. eonukwug@rx.umaryland.edu.
authors.forename: Eberechukwu
authors.initials: E
authors.lastname: Onukwugha
authors.affiliation: College of Pharmacy, Mercer University, Atlanta, GA, USA.
authors.forename: Jacquelyn
authors.initials: J
authors.lastname: McRae
authors.affiliation: Department of Pharmaceutical Health Services Research, School of Pharmacy, University of Maryland, 220 Arch Street, Baltimore, MD, 21201, USA.
authors.forename: Alex
authors.initials: A
authors.lastname: Kravetz
authors.affiliation: School of Pharmacy, Notre Dame of Maryland University, Baltimore, MD, USA.
authors.forename: Stefan
authors.initials: S
authors.lastname: Varga
authors.affiliation: Department of Pharmaceutical Health Services Research, School of Pharmacy, University of Maryland, 220 Arch Street, Baltimore, MD, 21201, USA.
authors.forename: Rahul
authors.initials: R
authors.lastname: Khairnar
authors.affiliation: Department of Pharmaceutical Health Services Research, School of Pharmacy, University of Maryland, 220 Arch Street, Baltimore, MD, 21201, USA.
authors.forename: C Daniel
authors.initials: CD
authors.lastname: Mullins
mesh_terms: D017048:Health Care Costs / Q000706:statistics & numerical data*; D006801:Humans