Comparative evaluation of erba Hb-vario with biorad D10 analyser for hemoglobin A1C quantitation

Selection of correct instrument for routine analysis by 'method evaluation' is a systematic stepwise assessment of the inherent analytical errors like imprecision, inaccuracy etc. of the analyser. As a final step, newer instrument that is being introduced in to the laboratory is compared with the existing one. We are presently communicating our method evaluation studies of Erba Hb-Vario against Bio-Rad DIO for glycosylated haemoglobin ([HbA.sub.1c]) quantitation. A blood sample with increased [HbA.sub.1c] (6.6%) was analysed 20 times to determine within-run and between-run precision and CV% were obtained 0.8 and 0.9%, respectively. Similar testing with another diabetic sample (11.2%) yielded CV% of 0.6%. Duplicate assays were performed in both the instruments on EDTA blood specimens from 60 patients. Regression analysis yielded the following statistical data: correlation coefficient 0.979, slope 0.986, and the Y-intercept 0. The proportional analytical error, as obtained from the slope, indicated each 1% value increase in Bio-Rad D10 will correspond to an increase by a factor of 0.986% in Erba Hb-Vario. However, Y-intercept showed absence of constant systematic error between two machines. Finally, the total error (TE) was calculated using the equation: TE = [absolute value of Bias%]+ Z x (Imprecision), considering Z = 2.33 at 99% confidence interval (p