Overuse of Laboratory Tests in Outpatient Care: A Retrospective Cross-Sectional Multilevel Analysis of Patterns, Predictors, and Financial Burden in Iran’s Health Insurance System

OBJECTIVES: Unnecessary laboratory testing, particularly nonadherent repeat tests, imposes significant financial and clinical burdens. This study aimed to quantify the financial burden and identify predictors of temporally noncompliant laboratory test utilization in outpatient care. METHODS: Administrative claims data from all eligible outpatients covered by the Health Insurance Organization of Khuzestan Province were analyzed for selected laboratory tests conducted between March 21, 2023, and March 20, 2024. Financial burden was calculated by aggregating test costs and partitioning shares between patients and insurers. Multilevel logistic regression assessed the influence of predictors on the likelihood of noncompliant test ordering. Intraclass correlation coefficients quantified variance attributable to clustering at the institutional level. RESULTS: Overall, 2.36% of the 1 294 623 laboratory tests were classified as temporally overused. Thyroid stimulating hormone (19.8%), triglycerides (17.5%), and cholesterol (16.2%) had the highest rates of temporal noncompliance, whereas HbA1c adherence exceeded 99%. The total financial burden of temporally noncompliant tests was $396 004, with patients bearing 78.1% and insurers 21.9%. Multilevel modeling showed that male patients had lower odds of noncompliant testing (OR = 0.87, 95% CI: 0.84-0.89), whereas male physicians had higher odds (OR = 1.45, 95% CI: 1.42-1.49). Public hospitals (OR = 0.68, 95% CI: 0.66-0.70) and comprehensive health centers (OR = 0.36, 95% CI: 0.34-0.38) were less likely to order temporally noncompliant tests than private settings. Intraclass correlation coefficient was 0.002, indicating minimal clustering effect. CONCLUSIONS: Temporal overuse of laboratory testing imposes substantial financial costs, predominantly on patients. Interventions targeting practices are essential to reduce unnecessary testing and improve equity in access.