Hemoglobin Genotype Distribution Among Filipinos: A Historical Systematic Review (1958–2025)

Abstract

Hemoglobin genotype distribution is a critical population-health indicator for guiding screening, genetic counseling, and anemia control, yet Philippine evidence has accumulated in a fragmented and method-dependent manner. This historical systematic review synthesized evidence on hemoglobin genotype distribution among Filipinos from 1958–2025, prioritizing population-based Philippine studies and incorporating historically important diaspora, referral, newborn screening, and molecular reports for contextual interpretation. Comprehensive searches of electronic databases, local journals, institutional repositories, and gray literature identified eligible studies reporting genotype frequencies with defined denominators; studies were appraised for quality and synthesized narratively by diagnostic era and population frame. Across six decades, α-thalassemia and β-thalassemia consistently emerged as predominant disorders, with hemoglobin E remaining clinically significant, particularly in coinheritance. Apparent variation in reported frequencies largely reflected diagnostic platforms, confirmation practices, and sampling frames rather than clear epidemiologic shifts. Molecular evidence converged on a limited mutation spectrum dominated by Southeast Asian (SEA) and Filipino (FIL) α-globin deletions and recurrent β-globin mutations, including the Filipino β⁰ deletion. Nationwide newborn screening marked a major inflection point toward population-level detection, though confirmatory and follow-up gaps persist.