Comparative evaluation of immunochemical methods for estimation of albumin in microalbuminuria

Three immuno assays namely radioimmunoassay (RIA), radial immunodiffusion (RID) and rocket immunoelectrophoresis (RIE) were compared for their performance and utility. The accuracy limits of the methods were compared and also between methods using RIA as the reference. Urine samples, from known diabetic patients with albumin concentration ranging from 2.5 mg/l to 120 mg/l were analysed by the three methods. The mean differences were only 0.91 mg/dl and 0.5 mg/dl respectively for RID vs RIA and rocket vs RIA which is not statistically significant. Excellent correlation was seen between RIA and RIE (r = 0.98) and also between RIA and RID (r = 0.97). Compared to RID, RIE required less time and was more precise. RIA is suited for assaying large sample loads yet not suited for laboratories receiving samples occasionally. For a small pathological laboratory with limited facility rocket electrophoresis may be the most suitable method taking into consideration accuracy, time and cost.