Free Versus Neutrophil-Bound Antibodies in 100 Consecutive Italian Children with Chronic Neutropenia.

Chronic neutropenia (CN) is defined as a blood absolute neutrophil count (NC) below 1500/ml, lasting for at least 6 months. We report the results of serological screening for anti-neutrophil antibodies, performed in our laboratory during 2002–2005, in 100 consecutive children affected from CN and followed in 4 Italian pediatric centers.

The patients, 65 males (m) and 35 females (f), had a median age of 18 months (range: 1–180). Both IgG bound to patient neutrophils (CD16+ cells) and the patient serum reactivity against healthy donor granulocytes (Direct and Indirect Granulocyte-Immunofluorescence Test, D-GIFT and I-GIFT) were assessed by flow-cytometry. The results are shown in the table, grouped according to the pattern of reactivity observed with D- and I-GIFT:

A NC above 1500/ μl on the day of serological screening was found in 5.5%, 22.4%, 0% and 35% of patients in groups 1, 2, 3 and 4, respectively. Secondary CN, usually in association with other autoimmune disorders or malignant diseases, was reported in 5.5%, 10.3%, 0% and 50% of patients in groups 1, 2, 3 and 4, respectively. Infections were present in 72%, 79%, 25% and 8% of patients in groups 1, 2, 3 and 4, respectively. In group 2, 50 of the 58 patients (86%), who didn’t show anti-neutrophil antibodies in their sera, presented neutropenia with concomitant infections. In these patients only D-GIFT was able to detect neutrophil antibodies.

Patients testing positive for I-GIFT had more severe neutropenia. Patients negative by both techniques were mostly found to have non-immunomediated neutropenia at clinical follow up. Although many laboratories perform only an indirect test to detect antineutrophil antibodies, our results suggest that direct test is more sensitive in identifying immunomediated chronic neutropenia.