title: Blood neutrophil counts in HIV-infected patients with pulmonary tuberculosis: association with sputum mycobacterial load.
abstract: BACKGROUND
  Increasing evidence suggests that neutrophils play a role in the host response to Mycobacterium tuberculosis. We determined whether neutrophil counts in peripheral blood are associated with tuberculosis (TB) and with mycobacterial load in sputum in HIV-infected patients.
  
  
  RESULTS
  Adults enrolling in an antiretroviral treatment (ART) clinic in a Cape Town township were screened for TB regardless of symptoms. Paired sputum samples were examined using liquid culture, fluorescence microscopy, and the Xpert MTB/RIF assay. Absolute neutrophil counts (ANC) were measured in blood samples. Of 602 HIV-infected patients screened, 523 produced one or more sputum samples and had complete results available for analysis. Among these 523 patients, the median CD4 count was 169×10(9)/L (IQR, 96-232) and median ANC was 2.6×10(9)/L (IQR, 1.9-3.6). Culture-positive pulmonary tuberculosis was diagnosed in 89 patients. Patients with TB had a median ANC of 3.4×10(9)/L (IQR, 2.4-5.1) compared to 2.5×10(9)/L (IQR, 1.8-3.4) among those who were culture negative (p<0.0001). In multivariable analyses, having pulmonary TB was associated with an adjusted risk ratio (aRR) of 2.6 (95%CI, 1.5-4.5) for having an ANC level that exceeded the median value (ANC ≥2.6×10(9)/L; p = 0.0006) and an aRR of 6.8 (95%CI, 2.3-20.4) for having neutrophilia defined by a neutrophil count exceeding the upper limit of the normal range (ANC >7.5×10(9)/L; p = 0.0005). Patients were then classified into four mutually exclusive groups with increasing sputum mycobacterial load as defined by the results of culture, Xpert MTB/RIF and sputum smear microscopy. Multivariable analyses demonstrated that increasing sputum mycobacterial load was positively associated with blood ANC ≥2.6×10(9)/L and with neutrophilia.
  
  
  CONCLUSIONS
  Increased blood neutrophil counts were independently associated with pulmonary TB and sputum mycobacterial burden in this HIV-infected patient group. This observation supports the growing body of literature regarding the potential role for neutrophils in the host response to TB.
authors.affiliation: School of Medicine and Health Sciences, The George Washington University, Washington, DC, United States of America. Kerkhoff@gwu.edu
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Kerkhoff
authors.forename: Robin
authors.initials: R
authors.lastname: Wood
authors.forename: David M
authors.initials: DM
authors.lastname: Lowe
authors.forename: Monica
authors.initials: M
authors.lastname: Vogt
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Lawn
mesh_terms: D000328:Adult; D060085:Coinfection; D005260:Female; D015658:HIV Infections / Q000097:blood* / Q000382:microbiology; D006801:Humans; D007958:Leukocyte Count; D008297:Male; D009504:Neutrophils; D012307:Risk Factors; D013019:South Africa; D013183:Sputum / Q000382:microbiology*; D014397:Tuberculosis, Pulmonary / Q000097:blood* / Q000382:microbiology