Hepatitis B Surface Antigen Seropositivity and Low Body Weight Are Correlated with Asymptomatic Neutropenia In the Thai Population

The etiology of asymptomatic neutropenia is unknown. We have conducted a community-based study to determine predisposing factors for asymptomatic neutropenia in the Thai population.

Blood specimens and self-report questionnaires (filled out with assistance from medical personnel) were collected from individuals in Bangkok and 4 surrounding provinces. Asymptomatic neutropenia was defined by an absolute neutrophil count of less than 1.5 × 10⁹/liter, in the absence of any symptoms or known risk factors. Patients with a history of malignancy were excluded. Subjects that met this criterion for neutropenia were examined for the presence of anti-HIV and anti-hepatitis C virus (HCV) antibodies, hepatitis B surface antigen (HBsAg), antinuclear antibody (ANA), rheumatoid factor (RF), thyroid dysfunction, reduced serum ferritin, and reduced serum vitamin B12 and folate; this panel of laboratory tests was also done on control subjects (4 controls for every 1 neutropenic case – see below), which were picked at random from the normal population and were matched for age, sex, site of survey, and underlying disease. Odd ratios (OR) were then computed for significant risk factors.

Overall, 7,180 individuals were included; 28 had neutropenia (0.39%, 95% CI 0.25–0.53). Based on answers to the questionnaire, the only factor correlating with neutropenia was low body weight (body mass index < 18.5 kg/m², p = 0.015); age, sex, site and period of survey, underlying disease, medications, herbal ingestion, food supplement, radiation exposure, family history of hematologic disease, alcohol consumption, history of drug abuse or exposure to chemical substance had no significant association with neutropenia. Additional tests on 25 of the neutropenic cases revealed positive findings for HBsAg (20%), anti-HCV antibody (12%), ANA (16%), RF (4%), hypothyroidism (4%), hyperthyroidism (14%) and hypoferritinemia (24%); none showed anti-HIV positivity, or low levels of serum vitamin B12 and folate. Of the 100 normal controls, 4% showed seropositive for HBsAg. HBsAg positivity was thus the significant risk factor associated with neutropenia (OR 6.0, 95%CI 1.48–24.34, p = 0.012).

HBsAg seropositivity is strongly associated with asymptomatic neutropenia in the Thai population. Low body weight is also correlated with the disorder, perhaps as a result of subtle nutritional deficiencies. Possible mechanisms that underlie neutropenia are currently being explored.

No relevant conflicts of interest to declare.