Clinical predictors of diagnostic testing utility in the initial evaluation of chronic kidney disease

Aim: No evidence-based approach to the evaluation of CKD has been established. We sought to identify clinical criteria to guide a rational diagnostic approach for the initial evaluation of CKD. Methods: We conducted a retrospective cohort study of 1487 patients presenting for initial evaluation of CKD over 3 years (1/2010-1/2013) to academic nephrology clinics. We utilized the electronic medical record to determine tests ordered, abnormal results and testing that affected diagnosis and/or management. Diagnostic and management yield of testing was defined as the percentage of tests that affected diagnosis and/or management. High yield for a given test was defined as an increased likelihood of the test affecting diagnosis and/or management. Results: We identified clinical criteria predictive of high yield for paraprotein-related testing (one of the following: history of monoclonal disease, high risk of CKD progression, hypercalcemia or haemoglobin < 10.6), and clinical criteria predictive of high yield for glomerulonephritis testing (one of the following: abnormal urine sediment, 3+ or greater hematuria or proteinuria > 500mg/gm). A prior history of hydronephrosis and renal artery stenosis was predictive of high yield of abnormal renal ultrasound. Higher yield of testing was associated with higher risk progression categories for ANA, SPEP, urine sediment, calcium, PTH, haemoglobin, iron and ferritin. We estimate that initial CKD evaluation costs range from $28 to $109 million/year in US-Medicare expenditure. Conclusion: Numerous tests without significant clinical utility are obtained in initial CKD evaluation. Identifying criteria that can guide diagnostic testing may lead to a more informed and cost-effective approach to evaluation.