[Current methodological problems in the determination of erythrocytes, hemoglobin and hematocrit].

Four instruments for the determination of RBC, Hb and PCV, with different degree of automation, have been compared in strictly routinary working conditions. Experimental protocols were designed in order to collect data for the assessment of both precision and accuracy: accuracy has been estimated by assuming the values obtained with the Coulter S as provisional reference values. In most instances, with particular reference to RBC, precision was higher with automated machines; however, Hb was quantitated with sufficient precision with a semi-automated technique and in the determination of PCV precision of the manual micro-centrifuge compared with precision of the automated instruments. As far as acuracy is regarded, collaborative experiments showed general agreement with the (provisional) reference values, with occasional occurrence of typical systematic errors in RBC and Hb determinations. The magnitude of the systematic error, however, was not constant with the same instrument in several analytical series. The whole of the results point out to the feasibility of obtaining clinically-significant analytical values with the several instruments tested. However good calibration and quality control procedures are necessary in order to maintain accuracy at acceptable levels. Improvement of precision is also needed in some instances.