Single or duplicate analysis for automated prothrombin time and activated partial thromboplastin time?

The introduction of automated coagulation analysers raises the possibility of performing routine coagulation tests as single rather than duplicate analyses. This study compares the duplicate results of the prothrombin time (PT) and activated partial thromboplastin time (aPTT) to that of a single result obtained by the MLA Electra 1000c using two different methods, The first method looks specifically at the difference between the mean duplicate result and the single result to determine if they alter patient management, This method found that two of 4152 PTs (0.048%) and two of 3047 aPTTs (0.065%) were clinically significant, The second method statistically assessed the agreement between the traditional mean duplicate result and the single test. This supported the introduction of single testing as the calculated 95% confidence intervals demonstrate that each result is interchangeable for purposes of clinical interpretation, These results supported the introduction of single testing for PT and aPTT estimation in our laboratory. The introduction of single testing was accompanied by changes to quality control and machine maintenance to ensure that the functions previously covered by duplicate testing were maintained. A strict protocol for repeat testing has also been adopted.