OUR EXPERIENCE WITH A NEW, RAPID, QUALITATIVE URINE TEST TO IDENTIFY PATIENTS WITH PERSISTENT COAGULATION ACTIVATION AFTER ELECTIVE HIP ARTHROPLASTY

Abstract

To target postoperative patients in need for prolonged pharmacologic thromboprophylaxis due to persistent coagulation activation, we developed and evaluated a qualitative test method, which detects the urinary excretion of prothrombin fragment 1+2 (uF1+2). The test was developed as a dip-stick device consisting of a one step rapid lateral flow immunoassay with visual readout on one test line and one control line. The assay time was between 5 and 10 minutes.

Spot urine samples were collected in 113 patients undergoing elective hip arthroplasty preoperatively and on day 5 after operation. Specimens were frozen immediately and stored until batch analysis. Pharmacologic thromboprophylaxis was administered according to national guidelines until day 7±2 after the operation. The results of the new dip-stick device were compared with the results of a laboratory based enzyme-linked-immunosorbent-assay (ELISA) method and a predetermined cut-off value. Patients were followed for development of vascular thrombotic complications/unexpected death until day 90 after the operation.

10 (8.8%) patients experienced an event during the study: 2 (1.8%) died unexpectedly and 8 (7.1%) had a vascular thrombotic event. All patients with clinical events had significantly raised postoperative levels of uF1+2. The clinical accuracy of the dip-stick test was acceptable with a sensitivity of 100% and a negative predictive value of 100%. Compared to the standard ELISA method the dip-stick test had a sensitivity of 93% and a specificity of 48%.

Laboratory ELISA analysis of urinary excretion of uF1+2 is neither feasible nor applicable in postoperative patients. Bed-side testing of persistent coagulation activation, however, could help to determine the need for prolonged thromboprophylaxis. The new dip-stick urine test was very easy to use, had a high negative predictive value and sensitivity and thus appears to be safe. However, the number of false positive test results prompts a fine-tuning of the test device. In terms of clinical applicability the test was acceptable. The study showed that about one third of the patients could be excluded from further extension of thromboprophylaxis beyond the first week.