Establishing hemoglobin A, F, A2 reference intervals in neonatal cord blood and clinical decision values for β-thalassemia genetic testing

OBJECTIVE: Reference intervals for hemoglobin fractions in neonatal cord blood have been reported; however, there is no consensus on population-specific reference intervals (RIs) and laboratory-derived clinical decision values (CDVs) to guide genetic testing. Therefore, we aimed to establish RIs for HbA, HbF, and HbA2 in neonatal cord blood using a big-data-based indirect method and to determine CDVs for neonatal β-thalassemia genetic testing. METHODS: In this retrospective study, we analyzed neonatal cord blood hemoglobin electrophoresis and β-thalassemia genetic testing data collected between January 2013 and November 2024. RIs for HbA, HbF, and HbA2 were established using an indirect method, and CDVs for β-thalassemia genetic testing were determined using receiver operating characteristic (ROC) curve analysis among neonates tested for β-thalassemia. RESULTS: Significant sex-related differences were observed in the RIs for neonatal cord blood hemoglobin. The RIs for HbA, HbF, and HbA2 were 7.8-29.4 %, 70.8-92.0 %, and 0-0.4 % in females and 6.9-27.3 %, 72.1-93.3 %, and 0-0.3 % in males, respectively. HbA2 was not a suitable marker for β-thalassemia genetic testing due to its extremely low levels in neonatal cord blood. The CDVs for β-thalassemia genetic testing were HbA ≤ 8.1 % and HbF ≥ 90.7 % in females and HbA ≤ 7.9 % and HbF ≥ 92.0 % in males, respectively. CONCLUSION: In this study, we established population-specific RIs for neonatal cord hemoglobin and proposed CDVs indicating that β-thalassemia testing is warranted when HbF ≥ 90.7 % in females or ≥ 92.0 % in males.