The Utility and Cost Effectiveness of Immediate Postoperative Laboratory Studies in Hip and Knee Arthroplasty.

BACKGROUND

Routine immediate postoperative laboratory studies, including metabolic panels and hematologic profiles, are commonly ordered after arthroplasty procedures. However, their values only occasionally influence management. This study investigated the clinical utility and value of these tests.

METHODS

A large retrospective cohort study of 18,935 patients spanning a 6-year period from 2008 to 2013 from a single high-volume institution was evaluated. Only immediate postoperative labs drawn on postoperative day 0 in the recovery room were included in the study. Complete blood counts (CBC) and basic metabolic panels (BMP) were reviewed, and ranges of abnormal were set for each lab test based on values significant enough to impact patient management. Cost effectiveness calculations were made based on current cost of the laboratory tests.

RESULTS

Actionably low hemoglobin values ( < 8 g/dL) were found in 1.44% of the overall cohort. Unilateral primary total knee arthroplasty was associated with the fewest hemoglobin abnormalities at 0.59%. Primary unilateral total hip arthroplasty was associated with abnormal hemoglobin values in 1.81% of cases. Significant electrolyte abnormalities were far less common, with hyperkalemia (> 6.5 mEq/L) in 0.19%, hyponatremia ( < 120 mEq/L) in 0.01% and elevated creatinine (> 2.0 mg/dL) was found in 0.25%. Hemoglobin values were calculated at a cost of $1,710 to detect a single significantly abnormal result. The cost to detect a single actionably abnormal BMP value was $1,000.

CONCLUSIONS

Routine immediate postoperative laboratory tests represent a high institutional cost and are seldom abnormal enough to warrant a change in patient management. The routine use of these tests can likely be safely eliminated in uncomplicated primary unilateral arthroplasty procedures.