Flow cytometric screening for paroxysmal nocturnal hemoglobinuria: An 8-year single-center experience from the Western Region of Saudi Arabia

Abstract: BACKGROUND: Paroxysmal nocturnal hemoglobinuria (PNH) is a rare clonal disorder, characterized by complement-mediated hemolysis, marrow failure, and thrombosis. Flow cytometry is the diagnostic gold standard, yet testing patterns remain poorly characterized in non-Western academic centers. OBJECTIVES: The objective of this study is to determine the frequency of PNH clone detection among submitted samples, describe the clinical and laboratory profiles of tested patients, and evaluate documented referral indications against recognized international testing guidance where documentation allowed. MATERIALS AND METHODS: This retrospective cohort study at King Abdulaziz University Hospital (Jeddah, Saudi Arabia) evaluated all unique peripheral blood samples submitted for PNH flow cytometric screening (January 2016–December 2023). Demographics, indications, ordering specialties, hematology involvement, and laboratory markers were analyzed. RESULTS: Among 59 unique patients (median age 36 years; 54.2% male; 4 repeat samples excluded), none met the clinical reporting threshold of ≥1% leukocyte clone size. A single sub-threshold clone (granulocytes: 0.62% and monocytes: 0.46%) was detected in a 60-year-old woman with aplastic anemia postantithymocyte globulin. Overall clone detection rate was 1.7% (1/59; 95% confidence interval [CI]: 0.04%–9.1%), with a clinically positive rate of 0% (0/59; 95% CI: 0%–6.1%). Documented indications included marrow failure/aplasia (20.3%) and hemolysis (18.6%). CONCLUSIONS: PNH clone detection was rare, limited to one sub-threshold clone in aplastic anemia. Frequent low-probability or undocumented referral indications highlight the need for hematologist-guided screening pathways to optimize test utilization.