SP02 | ANOMALOUS HEMATOLOGICAL PARAMETERS REVEALING HOMOZYGOUS HEMOGLOBIN C IN A β-THALASSEMIA BACKGROUND

β-thalassemia and cold agglutinins are hematological disorders that can present significant clinical challenges, particularly when associated with an additional hemoglobin variant. Here, we describe a case of a woman diagnosed with β-thalassemia and Raynaud's syndrome, further complicated by the presence of a hemoglobin C (HbC) variant revealed in our laboratory. The patient underwent for a routine blood tests. Complete blood count (CBC) and HbA1c samples were analyzed. The CBC, performed on a Sysmex XN 9000, revealed an MCV <60 fL, HGB 100 g/L, and a markedly elevated MCHC >2000 g/L, persisting after 1-hour incubation at 37°C to exclude cold agglutinins. The HbA1c analysis on Tosoh G11 was uninterpretable due to an interfering hemoglobin variant. Given the complexity of data interpretation, the patient was contacted again for a new, worm blood sampling with the analysis performed immediately after collection. However, MCHC remained elevated (2512 g/L), normalizing only after 4.5 hours of incubation. HGB and MCV values were stable throughout. HbA1c remained altered: initially 9 mmol/mol, HbF 0.8%, and a variant with a migration time of 0.8 min. Post-incubation, HbA1c has slightly increased to 16 mmol/mol. Hemoglobin electrophoresis and peripheral smear were performed on both fresh and incubated samples. Tosoh G11 analysis showed a low total hemoglobin area and identified homozygous HbC variant (77%) and elevated HbA2 (7.5%), indicating a coexisting thalassemic pattern. This variant, not previously reported in the patient's history, explains the findings. Homozygous HbC typically causes mild to moderate hemolytic anemia (100–120 g/L), high MCHC due to intracellular crystallization, and target cells on smear. This case illustrates how unusual lab results, initially suggestive of pre-analytical error, may be signal underlying pathology. When results persist after verification, a multidisciplinary, critical approach is essential for accurate interpretation and patient care.