Hemoglobin clinical decision limits: Chasing the numbers

Background The interpretation of hemoglobin (Hb) values in clinical practice involves both absolute thresholds and relative changes, yet alignment between clinical decision limits (CDLs) and laboratory quality control (QC) thresholds is unclear. This study aimed to compare published CDLs for Hb used in diagnosis and treatment with those applied in laboratory internal QC processes. Methods A literature search was conducted in PubMed (2018–2023) targeting adult populations. Eligible studies reported specific Hb thresholds or clinically relevant changes; case reports, case-control studies, and papers lacking these data were excluded. Results Out of 507 initial articles, 131 met eligibility criteria. Among these, 121 referenced significant changes in Hb values, with a mean change of 1.08 g/dL (range: 0.50–3.50 g/dL). The most frequently cited clinically meaningful change was 2.00 g/dL. Conversely, changes under 0.40 g/dL (mean 0.39 g/dL) were generally considered clinically insignificant. Transfusion thresholds were consistently reported at 7.00–8.00 g/dL. Values of 10.00, 11.50, 12.00, and 13.00 g/dL were cited across studies involving CKD hemodialysed and non-hemodialysed patients, anemia, or patient stratification. Conclusions There is substantial heterogeneity in reported Hb CDLs across clinical contexts. Current QC thresholds may overlook variations important to clinicians. Harmonizing QC strategies with clinical practice could enhance measurement reliability and patient care.