TDK conference 2008

One of the most important elements in laboratory diagnosis of kidney diseases is to know the creatinine concentration in the blood serum. We wanted to introduce a new, one-way photometer in emergency measurement of the creatinine at the Department and Clinic of Internal Medicine, Faculty of Veterinarian Science, Szent István University that has not been applied in veterinary practice so far.

The precision of the traditional creatinine determination providing fast results and that is based on Jaffé method was evaluated on Microlab 50 and on Lab-Analyse (Orvostechnika Ltd., Budapest) clinical chemistry analyzers. We validated both of the instruments with numerous measurements. In the knowledge of the results of the internal quality control methods we performed a factor-modified calibration on the Microlab 50 for precise determination of creatinine in serums containing pathologically high values.

We examined control serums with 4 different creatinine concentration (low : 70 μmol/L, normal: 137 μmol/L, elevated: 312 μmol/L, high:624 μmol/L) in series of 15-15 samples.

In the case of Microlab 50 the reproductibility (precision) were appropiate (<7% in each serums) while the accuracy (bias) of the instrument was substantially high in the serums with extremely high creatinine concentration (-20.11%). Since we wish to use this instrument in urgent medical attendance, when pathologic values most commonly occurs, in this concentration-range we needed to change the built-in factor of the device. After the theoretically calculated factor modification of 10%, the bias in samples containing extremely high creatinine has decreased close to quarter size and its precision remained appropriate. We proved with the examination of 15 further serum samples with extremely high creatinine concentration that factor modification the Microlab 50 provided accurate results in the clinically important, azotaemiac measuring range.

Based on our experiences we recommend using Microlab 50 analyzer for urgent creatinine evaluation.