Two new artifacts in automated coagulation testing.

Abstract

Two artifacts were noted during the routine use of the Sherwood Lancer Coagulyzer. The first was that prothrombin times for 44 patients were greater than 90 sec on the Sherwood instrument, but were significantly shorter using reference methods. All 44 patients had subnormal fibrinogen values. Continuous optical density tracings during clotting performed for 11 patients demonstrated low slopes and amplitudes. For the three patients tested, the addition of fibrinogen corrected prothrombin times to values similar to those obtained on the Bio-Data instrument. Twenty-four of the patients subsequently died, 20 within three weeks of the observation of the artifact. The second artifact was that activated partial thromboplastin times for 12 patients were 9 sec on the Sherwood instrument, but were either normal or prolonged when using reference methods. Continuous tracings performed for nine patients demonstrated early optical density increases before clotting, which were responsible for the spurious values. Eleven of the 12 patients were hypoalbuminemic, and nine of the ten tested had elevated IgM levels. For seven patients, the artifact disappeared with in-vitro correction of hypoalbuminemia. Far from being weaknesses of the Coagulyzer, these artifacts may lead to the discovery of unsuspected, clinically significant laboratory information.