ABSTRACT
The automated 0.cresophthalein complexone dye method was recently introduced in the calcium chemistry module of the ASTRA-8 system present in Ain Shams University Hospital. This method was evaluated in comparison with the atomic absorption spectrophotometer reference method. Quality control material [normal and pathological levels] and 40 patient samples were used in the evaluation study. The coefficients of variation for the within batch precision were 1.5% and 1.1%, while those for the day to day precision were 3.2% and 2.3% for the normal and pathological levels respectively. Accuracy study showed minimal bias [0.12 mg/dl] and no statistically significant difference was observed between the two methods. Recovery was excellent. Linearity was 4.5 - 13 mg/ dl. No interference was detected by magnesium, while haemoglobin at a level of 1 g/dl showed a decrease in calcium concentration with an average of 0.6 mg/dl. The throughput was 70 samples/ hour, Very small sample size [12 micro l] or reagent [150 micro l] was required. There was good correlation between the ASTRA calcium method and atomic absorption spectrophotometry [Y = 1.97 + 0.8 X r=0.92]. The goals of analytical reliability, simplicity and convenience were nearly achieved by the -ASTRA-8 calcium method