Supplementing claims data with outpatient laboratory test results to improve confounding adjustment in effectiveness studies of lipid-lowering treatments

• Published in: BMC medical research methodology Vol. 12; no. 1; p. 180
• Main Authors: Schneeweiss, Sebastian, Rassen, Jeremy A, Glynn, Robert J, Myers, Jessica, Daniel, Gregory W, Singer, Joseph, Solomon, Daniel H, Kim, Seoyoung, Rothman, Kenneth J, Liu, Jun, Avorn, Jerry
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 26-11-2012; BioMed Central; BMC
• Subjects: Adult; Aged; Aged, 80 and over; Analysis; Analysis and chemistry; Anticholesteremic agents; Azetidines - therapeutic use; Blood; Claims adjustment (Insurance); Confounding; Diagnostic Tests, Routine; Drug Combinations; Electronic health records; Ezetimibe; Ezetimibe, Simvastatin Drug Combination; Female; Glycated Hemoglobin A - drug effects; Health care policy; Health insurance; Heart attacks; Hospitals; Humans; Hydroxymethylglutaryl-CoA Reductase Inhibitors - therapeutic use; Hypolipidemic Agents; Imputation; Insurance Claim Review; Insurance claims data; Laboratory test results; Lipid lowering therapy; Lipids - blood; Lipoproteins, HDL - blood; Lipoproteins, HDL - drug effects; Lipoproteins, LDL - blood; Lipoproteins, LDL - drug effects; Low density lipoproteins; Male; Medical examination; Medical records; Medicare Part B; Medicare Part C; Middle Aged; Patients; Pharmacoepidemiology; Product safety; Serum lipid levels; Simvastatin; Simvastatin - therapeutic use; Statin; Studies; Treatment outcome; United States; Womens health; Young Adult; United States
• ISSN: 1471-2288; 1471-2288
• DOI: 10.1186/1471-2288-12-180

Adjusting for laboratory test results may result in better confounding control when added to administrative claims data in the study of treatment effects. However, missing values can arise through several mechanisms.
We studied the relationship between availability of outpatient lab test results, lab values, and patient and system characteristics in a large healthcare database using LDL, HDL, and HbA1c in a cohort of initiators of statins or Vytorin (ezetimibe & simvastatin) as examples.
Among 703,484 patients 68% had at least one lab test performed in the 6 months before treatment. Performing an LDL test was negatively associated with several patient characteristics, including recent hospitalization (OR = 0.32, 95% CI: 0.29-0.34), MI (OR = 0.77, 95% CI: 0.69-0.85), or carotid revascularization (OR = 0.37, 95% CI: 0.25-0.53). Patient demographics, diagnoses, and procedures predicted well who would have a lab test performed (AUC = 0.89 to 0.93). Among those with test results available claims data explained only 14% of variation.
In a claims database linked with outpatient lab test results, we found that lab tests are performed selectively corresponding to current treatment guidelines. Poor ability to predict lab values and the high proportion of missingness reduces the added value of lab tests for effectiveness research in this setting.