Cytogenetic Evaluation of APL Cases Using Karyotyping and FISH and Its Correlation with Overall Clinical Outcomes: A Retrospective Laboratory-Based Study.

Abstract

Objectives: Acute promyelocytic leukemia (APL) is cytogenetically characterized by the t(15;17)(q22;q21) translocation generating the PML::RARA fusion gene. Accurate laboratory diagnosis is essential for disease confirmation and prognostic prediction. In our cytogenetics laboratory, conventional GTG-banded karyotyping and fluorescence in situ hybridization (FISH) are routinely performed for all APL-suspected cases received from the chemotherapy unit of The Gujarat Cancer and Research Institute, Ahmedabad, after bone marrow/IPT requisitions. To document the cytogenetic abnormalities detected in APL-suspected cases using karyotyping and FISH, and to analyze their association with overall patient survival outcomes. This retrospective study included 32 APL-suspected cases referred to our laboratory. Each case underwent conventional cytogenetic analysis and FISH for the PML::RARA fusion. Clinical outcomes (Normal/Recovered, Discharged/Stable, Expired) were obtained from hospital records solely for correlation. Statistical analysis using SPSS included cross-tabulation and chi-square testing to assess the association between FISH status and patient outcomes. FISH detected PML::RARA fusion in 78.1% of cases (25/32), while 21.9% (7/32) exhibited negative or variant fusion patterns. All successful karyotyping studies demonstrated t(15;17), with occasional additional abnormalities. FISH-positive patients showed significantly better recovery rates (60%) compared to none among FISH-negative/variant cases. The association between FISH status and outcome was statistically significant (χ² = 11.165, p = 0.004). Cytogenetic evaluation using karyotyping and FISH provides essential diagnostic and prognostic insight in APL-suspected cases. FISH positivity strongly correlates with favorable outcomes, underscoring its value in routine diagnostic workflows.