Evaluation of the Hitachi 717 analyser

The selective multitest Boehringer Mannheim Hitachi 717 analyser was evaluated according to the guidelines of the Comisión de Instrumentación de la Sociedad Española de Química Clinica and the European Committee for Clinical Laboratory Standards. The evaluation was performed in two steps: examination of the analytical units and evaluation in routine operation. The evaluation of the analytical units included a photometric study: the inaccuracy is acceptable for 340 and 405 nm; the imprecision ranges from 0.12 to 0.95% at 340 nm and from 0.30 to 0.73 at 405 nm, the linearity shows some dispersion at low absorbance for NADH at 340 nm, the drift is negligible, the imprecision of the pipette delivery system increases when the sample pipette operates with 3 μl, the reagent pipette imprecision is acceptable and the temperature control system is good. Under routine working conditions, seven determinations were studied: glucose, creatinine, iron, total protein, AST, ALP and calcium. The within-run imprecision (CV) ranged from 0.6% for total protein and AST to 6.9% for iron. The between run imprecision ranged from 2.4% for glucose to 9.7% for iron. Some contamination was found in the carry-over study. The relative inaccuracy is good for all the constituents assayed.


Introduction
The Boehringer Mannheim Hitachi 717 is a selective multichanel analyser with a theoretical throughput of 750 tests per hour (with electrolytes, during routine operation). The evaluation reported here was carried out according to the guidelines of the European Committee for Clinical Laboratory Standards (ECCLS) [1] and the protocol of the Comisi6n de Instrumentaci6n de la Sociedad Espafiola de Qufmica Clfnica (SEQC) [2].
The evaluation of the analytical units included a photometric study: inaccuracy, imprecision, drift and linearity, together with the imprecision of the pipette delivery system and the temperature control system. Imprecision (within-and between-run), carry-over and relative inaccuracy were studied under routine working conditions. Reagents Non-standard abbreviations: BM, Boehringer Mannheim; TCN, Technicon; K, Knickerbocker; B, Behring; AST, aspartate aminotransferase (E.C. 2.5.1.2); ALP, alkaline phosphatase (E.C. 3 arranged to be around 0"500. In both experiments, the standard deviation and coefficient of variation were calculated from 30 successive determinations.

Temperature control
The warm-up time was studied making readings every 10 s, until three consecutive readings with a deviation of +0" C were obtained. Thirty readings were then made at 20-s intervals for 10 min. The mean, variance and coefficient of variation were calculated. For evaluation of the system under working conditions,, the parameters studied were as follows.

Imprecision
Within the same run, thirty samples of control sera were tested at three levels, in order to study the within-run imprecision. To evaluate the between-run imprecision a further thirty samples were distributed in different runs.
Specimen-independent carry-over All combinations of method sequences were checked in order to study the reagent probe carry-over, using a pool of specimens in a pre-determined sequence run on three different days. The carry-over effect measured was compared with twice the within-run imprecision of the  Sample-related carry-over Following a permutation order, two control samples with different concentrations were distributed along the sample disk. Three high specimens followed by three low specimens were processed and the carry-over ratio (k) was calculated. A mean value for ten determinations of k was obtained [3].

Method comparison with patients' specimens
We analysed 100 fresh human sera (in different analytical series) covering the entire analytical range for each of the seven analytes, with the Hitachi 717 and the RA-1000 and Ultrolab-Aurora comparison instruments. The statistical evaluation was done by a non-parametric method of Passing and Bablok [4,5].
Results and discussion
Temperature control Testing each 10 s, the warm-up time to reach 3 7 C was 12 min. An additional time of 3 min 40 s must be considered for initialization of the device.
The main temperature attained was 36-8C and the coefficient of variation was 0-08%. The variances found were smaller than those of the thermometer used. The temperature control system is good, although the time to attain a stable temperature is long. Imprecision Table 6 summarizes the results of the within-run and between-run imprecision studies. The within-run imprecision is acceptable for all the analytes assayed. The between-run imprecision is acceptable for all the analytes assayed except iron. Table 8. Relative inaccuracy with human sera on (y) Hitachi 717 and (x) comparison instrument: (1) Ultrolab-Auro.ra, (2) RA 1000 (n 100).
Regression analysis (y bx + a) Specimen-independent carry-over In the study of the reagent probe carry-over, possible contamination of total protein with iron was found. Possible washing unit-related contamination in the sequence from creatinine to total protein was also detected.
The results reflect good agreement with the comparison instruments except for creatinine; we found (p < 0"05) some proportional and constant differences between the two analytical methods.