[Clinical and Laboratory Characteristics of Cold Agglutinin Disease Patients with Positive Results of Acidified-Serum Lysis Test].

Objective: To analyze the clinical features and laboratory characteristics of patients with cold agglutinin disease (CAD)/cold agglutinin syndrome (CAS) who were positive for acidified-serum lysis test (Ham test), and to compare them with Ham test negative CAD/CAS patients and paroxysmal nocturnal hemoglobinuria (PNH) patients, in order to provide references for the differential diagnosis of these diseases.

Methods: 53 patients diagnosed with CAD/CAS and 67 patients diagnosed with classic PNH in our hospital from January 2015 to December 2020 were retrospectively analyzed. The patients were grouped according to clinical diagnosis and results of cold agglutinin test (CAT), direct antiglobulin test (DAT), Ham test and PNH clone detection. The clinical and laboratory characteristics of each group were compared.

Results: The patients were grouped as follows: Ham^- CAD/CAS group, CAD/CAS patients negative for Ham test (n=36); Ham⁺ CAD/CAS group, CAD/CAS patients positive for Ham test (n=17); classic PNH group (n=67). Compared with the classic PNH group, the Ham⁺ CAD/CAS group had a higher median age (P =0.024), weaker positivity of Ham test, higher positive rates of CAT and DAT, and lower positive rate of PNH clone detection (all P <0.001). The proportions of patients with splenomegaly and cyanosis in Ham⁺ CAD/CAS group were significantly higher than those in classic PNH group (P =0.002 and P <0.001). Ham⁺ CAD/CAS group displayed lower red blood cell count (RBC) and lactate dehydrogenase (LDH) level (P =0.007 and P <0.001), and higher mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), and indirect bilirubin (IBIL) level (P =0.003, P =0.004 and P =0.006) than those in classic PNH group. The levels of serum complement C3 and C4 in Ham⁺ CAD/CAS group were lower than those in classic PNH group (P =0.001 and P <0.001). The positive rate of urinary occult blood in Ham⁺ CAD/CAS group was lower than that in classic PNH group (P =0.010). The clinical and laboratory characteristics of Ham⁺ CAD/CAS group were similar to those of Ham^- CAD/CAS group, except for median age, hemoglobin (Hb), MCHC, mean corpuscular volume (MCV), reticulocyte ratio (Ret), Ham test results, DAT positive types, and proportion of splenomegaly.

Conclusion: Some clinical features and laboratory indicators of CAD/CAS patients with positive results of Ham test are different from those of classic PNH patients, but relatively similar to those of CAD/CAS patients with negative results of Ham test. These results may provide a reference for differential diagnosis of related diseases.