ON THE CORRECT DETERMINATION OF REFERENCE VALUES FOR SERUM ANTIBODIESAGAINST PIGEON SERUM ANTIGEN USING A GROUP OF HEALTHY BLOOD-DONORS

An enzymatic immunoassay was developed in order to evaluate the statis tical distribution of IgG serum antibodies against pooled pigeon sera antigen in 102 healthy blood donors (HBD). A non-normal distribution w as obtained as demonstrated by abnormal values of skewness (2.02) and kurtosis (6.50), A cut-off point (0.120) was determined from the mean plus 2 standard deviations of the optical density values obtained in t he HBD group. This value was able to segregate 94% of subjects. Howeve r, when calculation of the mean less 2 SD was performed to delimit 95% of the samples, an aberrant negative value was obtained. In contrast, when the nonparametric method of percentile calculation was applied, an optical density value of 0.130 discriminated 97.5% of samples. In a ddition, the interval between p97.5 and p2.5 delimited 95% of samples, We conclude that when reference values and cut-offpoint are determine d from an enzymatic immunoassay, careful analysis of the statistical d istribution of reference values is necesary in order to avoid the inap propriate application of parametric procedures as demonstrated in this study for antibodies against pigeon serum antigens.