Pediatric Laboratory Medicine
Core concepts
Know pediatric-specific laboratory issues: age-dependent reference intervals (especially for hemoglobin, leukocytes, and chemistries), capillary vs venous sampling, and the effect of hemolysis and small volumes. Understand neonatal hematology-physiologic anemia, physiologic nadir, and the high fetal hemoglobin fraction. Master transfusion medicine in neonates: small-volume transfusions, irradiated/leukoreduced products, CMV-safe blood, and the risk of transfusion reactions.
In microbiology, understand culture yield limits, the role of molecular panels, and contamination pitfalls. In chemical pathology, know newborn screening cutoffs, bilirubin interpretation (physiologic vs pathologic jaundice, direct vs indirect), and glucose homeostasis. Genomic pathology includes variant interpretation and reporting.
Traps
Examiners exploit non-age-adjusted reference intervals-a normal adult hemoglobin may be abnormal in a neonate. Another trap: misinterpreting physiologic jaundice as pathologic; timing and fraction matter. Also, small specimen volumes can cause dilutional errors and spurious results.
Worked example / rule of thumb
A 3-day-old with jaundice and indirect hyperbilirubinemia, otherwise well: physiologic jaundice. Rule of thumb: "Always interpret pediatric labs against age-specific intervals, and check the fraction before the total."