[Clarification of anemia: quality control in the general practice laboratory].

In mailed blood samples from 602 adult patients with beta-thalassaemia trait, a mean MCH value of 20.5 pg with a 2 s range of 17-24 pg was found. These values are identical to those determined in fresh blood samples. Furthermore, the Gaussian distribution indicates that reliable values are obtained in mailed blood samples. From patients with previous blood analyses in hospital and biochemical laboratories the MCH values of the foreign laboratories correlated well with our results (r = 0.87). On the other hand, a poor correlation was observed for private practice laboratories (r = 0.71). The difference of the two correlation coefficients is statistically highly significant (p less than 0.001). There is clearly a need for MCH quality control in the laboratories of many practitioners. Continuous quality control by means of values from healthy persons and the use of stabilized control blood is recommended.