Is there variation in utilization of preoperative tests among patients undergoing total hip and knee replacement in the US, and does it affect outcomes? A population-based analysis.

Study Objective: To describe recent practice patterns of preoperative tests and to examine their association with 90-day all-cause readmissions and length of stay.

Design: Retrospective cohort study using the New York Statewide Planning and Research Cooperative System (SPARCS).

Setting: SPARCS from March 1, 2016, to July 1, 2017.

Participants: Adults undergoing Total Hip Replacement (THR) or Total Knee Replacement (TKR) had a preoperative screening outpatient visit within two months before their surgery.

Interventions: Electrocardiogram (EKG), chest X-ray, and seven preoperative laboratory tests (RBCs antibody screen, Prothrombin time (PT) and Thromboplastin time, Metabolic Panel, Complete Blood Count (CBC), Methicillin Resistance Staphylococcus Aureus (MRSA) Nasal DNA probe, Urinalysis, Urine culture) were identified.

Primary And Secondary Outcome Measures: Regression analyses were utilized to determine the association between each preoperative test and two postoperative outcomes (90-day all-cause readmission and length of stay). Regression models adjusted for hospital-level random effects, patient demographics, insurance, hospital TKR, THR surgical volume, and comorbidities. Sensitivity analysis was conducted using the subset of patients with no comorbidities.

Results: Fifty-five thousand ninety-nine patients (60% Female, mean age 66.1+/- 9.8 SD) were included. The most common tests were metabolic panel (74.5%), CBC (66.8%), and RBC antibody screen (58.8%). The least common tests were MRSA Nasal DNA probe (13.0%), EKG (11.7%), urine culture (10.7%), and chest X-ray (7.9%). Carrying out MRSA testing, urine culture, and EKG was associated with a lower likelihood of 90-day all-cause readmissions. The length of hospital stay was not associated with carrying out any preoperative tests. Results were similar in the subset with no comorbidities.

Conclusions: Wide variation exists in preoperative tests before THR and TKR. We identified three preoperative tests that may play a role in reducing readmissions. Further investigation is needed to evaluate these findings using more granular clinical data.