Bridging the diagnostic gap in CLL through TP53 molecular diagnostics in sub-Saharan Africa

ABSTRACT Chronic lymphocytic leukaemia (CLL) is increasingly recognised in sub-Saharan Africa, yet TP53 mutation analysis essential for risk stratification remains largely inaccessible, and the long-read sequencing platforms suited to such settings carry an error profile that can generate false pathogenic calls at low variant-allele frequencies. In a prospective cross-sectional study of 32 treatment-naïve patients with CLL at a tertiary centre in Tanzania, we performed targeted TP53 sequencing on the Oxford Nanopore platform with a validation framework combining dual variant-caller concordance, strand-bias analysis, and orthogonal Illumina MiSeq confirmation. Two of four candidate pathogenic variants were identified as strand-biased artifacts and excluded; pathogenic TP53 mutations were confirmed through cross-platform validation in 2 of 32 patients (6.25%; 95% CI 0.8-20.8%), a codon 249 hotspot missense variant (p.Arg249Gly) and a splice-donor variant (c.993+2T>A), both concordant across platforms. Most patients presented symptomatically after a prolonged diagnostic interval (median 13.7 months), with advanced-stage disease in a substantial proportion (47% Rai III-IV; 44% Binet C). These data demonstrate that rigorous, cross-platform-validated TP53 analysis is feasible at point of care in Tanzania, with a pathogenic frequency within the range reported in European cohorts and provide both a validation framework for long-read variant detection and a foundation for molecular risk stratification in CLL care across sub-Saharan Africa.