Detecting failed WBC-reduction processes: a quality assurance program introduced in a blood center.

BACKGROUND: Pragmatic yet statistically valid quality assurance (QA) programs are necessary so that blood centers can select, validate, and monitor their WBC-reduction processes. A QA system for WBC-reduction processes based on the practical application of statistical theory within a large blood center was developed. The system identifies parameters for procedure and component evaluation and provides sample size and formatting suggestions. STUDY DESIGN AND METHODS: Analyses of both procedure and component performance were undertaken during the purchase, validation, and control of filtration and apheresis WBC-reduction processes at Blood Centers of the Pacific from 1997 through 1999. QA analysis was categorized on the basis of whether the process was new to the organization or was a modification of a previously validated system. The numbers of samples necessary to consistently detect failure in platelet yield, unit volume, pH, and WBC count was statistically determined by parametric and nonparametric techniques. RESULTS: Parametric analysis (power analysis) of the mean +/- SD of smaller numbers of samples was highly sensitive to shifted distributions, but only if the shift was normally distributed. Nonparametric analysis, necessary when the nature of the underlying distribution is unknown, suggested a minimal sample of 40 was required to achieve high confidence that significant bimodal failure (a secondary population with WBCs 5% above the cutoff) would be detected. CONCLUSION: A QA system, developed for the evaluation of new or revised WBC-reduction processes, was based on statistical analysis of normally and non-normally distributed process failure. The number of samples was determined that allowed the achievement of confidence and tolerance levels considered appropriate within the blood center. Suggestions for outlier evaluation and a format for performance documentation have also been developed. To better define blood center quality goals, further research is necessary on donor and component biologic variability and the most significant modes of WBC-reduction process failure.

Prevalence of ABO maternal-infant incompatibility in Asians, Blacks, Hispanics and Caucasians.

Previous studies suggest that race is a risk factor in ABO hemolytic disease of the newborn (ABO-HDN). In order to compare the prevalence of ABO-HDN in Asian, Black, Hispanic and Caucasian infants, we studied 10,611 consecutive births at one hospital over a 6-year period. Among group A infants born to group O mothers, the prevalence of positive DAT differed among the four groups (p = 0.007), and was highest in Asians (50%) and lowest in Caucasians (31%). However, the proportions of infants who required exchange transfusion were not different (p = 0.351). Among group B infants born to group O mothers, the prevalence of positive DAT was not different among the four groups (p = 0.26) and none of these 166 group B infants with a positive DAT result required exchange transfusion. Our findings suggest that there are small ethnic differences in the prevalence of positive DAT results in group A infants born to group O mothers, but the prevalence of clinical disease which requires exchange transfusion does not differ significantly among Asian, Black, Hispanic and Caucasian infants.

Autoantibodies mimicking anti-Jkb plus anti-Jk3 associated with autoimmune hemolytic anemia in a primipara who delivered an unaffected infant.

A serum sample from a nontransfused 25-year-old Caucasian primipara contained weak anti-Jkb plus anti-Jk3. The direct antiglobulin test on the patient's red cells was strongly positive. Anti-Jkb was recovered in a heat eluate. An ether eluate contained anti-Jk3. Her red cells types as Jk(a-b+)Jk:3. The anti-Jkb and anti-Jk3 reactivity was completely absorbed both by red cell samples lacking and red cells possessing the corresponding antigens, indicating these antibody specificities to be of the mimicking variety. At 41 weeks gestation she delivered a normal, healthy infant with no detectable serum or cell bound antibody.