Age-stratified CD19+ B-cell reference values in children and adolescents—a systematic review and meta-analysis

BACKGROUND: B-cell reference values currently lack harmonization and are inconsistently defined. OBJECTIVE: B cells in healthy children and adolescents (age range, 0-18 years). METHODS: B cells in healthy children from 2000 to 2025 (final search in March 2025). Records were independently screened and assessed for quality by 3 investigators. Data for lower limit of normal (lower limit of 95% reference interval) were analyzed and compared for different age groups. RESULTS: B-cell values differed according to the age of the child. We identified 5 distinct age groups and corresponding values of lower limit of normal. In children younger than 6 years, B-cell values were consistently different from values that have been reported for adults. CONCLUSION: B-cell values can be used for standardized clinical monitoring of B-cell recovery to normal values after CD19-depleting therapy.