Studies on the quality of specimens obtained by skin puncture of children 1. Tendency to hemolysis, and hemoglobin and tissue fluid as contaminants.

When preferred skin-puncture and blood-collecting techniques were used, the mean artifactually produced hemoglobin in 417 samples of plasma from pediatric patients was 260 mg/L. Highest values occurred exclusively in newborns, 0 to 13 days old (n = 176; mean, 390 mg/L), one-third of whom were premature. The highest value was 1470 mg/L. Only 3% of the samples exceeded 1000 mg/L. After 13 days, technically produced hemolysis is about the same as that for adult plasma (less than 200 mg/L). When skin-puncture and blood-collecting techniques are faulty--e.g., from excessive squeezing at the puncture site--plasma K and hemoglobin may be increased in the newborn to 13-day-old infant, and occasionally in older subjects. By determining plasma hemoglobin, K, blood hemoglobin, and hematocrit the contribution of "tissue fluid" is readily calculated. With excessive squeezing at the sampling site, tissue fluid sometimes contaminates plasma with hemoglobin and K, particularly in the youngest group. Values for alanine and aspartate aminotransferases, lactate dehydrogenase, inorganic P, and Na were little altered, even with squeezing, a fact particularly surprising for the enzymes, which are known to be present in markedly higher concentrations in erythrocytes and other tissues. Our data validate the Elson--Ivor--Gochman method (Am. J. Clin. Pathol. 69: 354-355, 1978) for quantitation of hemoglobin in plasma.