An evaluation of the Du Pont aca IV: does it meet medical needs?

A new bench-top analyzer from Du Pont, the "aca IV," was evaluated. To do so, we performed 10 different tests during an eight-week test period. The instrument is very precise (CVs less than 2%), results agree well with those obtained with the older acas (II and III), linearity is good in the clinically important ranges, and there is very little drift or carryover. From a medical-needs viewpoint, we found the analyzer satisfactory for all tests except possibly for calcium, for which the medical-needs criteria are so strict that few laboratories can meet them. We reached the latter conclusions by using a statistical model, described here, and from the predictive value of an abnormal test for populations with various prevalences of disease.