title: Sputum smear concentration may misidentify acid-fast bacilli as Mycobacterium tuberculosis in HIV-infected patients.
abstract: BACKGROUND
  Tuberculosis (TB) diagnosis in most resource-limited settings still depends on smear microscopy for identification of acid-fast bacilli (AFB). However, recently developed molecular diagnostics that test for the presence of Mycobacterium tuberculosis (Mtb) DNA have been shown to be superior for confirmation of TB diagnosis.
  
  
  METHODS
  At regular clinical visits over a 12-month period, we collected sputa from HIV-infected patients presenting with signs or symptoms of TB at 2 Nigerian clinics. Sputa were stained for AFB and tested using the Genotype MTBDRplus to confirm the presence of Mtb. Other species were identified using 16S rRNA sequence.
  
  
  RESULTS
  In 56% (233/415) of AFB-positive patients, Mtb was confirmed. The patients on antiretroviral therapy were less likely than those not on antiretroviral therapy to be infected with Mtb [odds ratio (OR) = 0.25, P = 0.003]. In a multivariate logistic regression model using clinical features and diagnostic results, abnormal respiratory findings on auscultation (OR = 3.28, P = 0.03) and a direct sputum smear grade >3/100 (OR = 6.4, 4.6, P < 0.02) were significant predictors of Mtb infection. Concentrated sputum smear was predictive of Mtb infection only at the highest grades (2+, 3+). Interestingly, among 65 samples that could not be confirmed for Mtb, 32 (49%) were found to contain other, possibly novel, actinomycetes, including atypical Mycobacteria, Rhodococcus spp, Nocardia spp, and Corynebacterium spp.
  
  
  CONCLUSIONS
  We conclude that concentrated sputum smears may misidentify other bacteria as Mtb in HIV-infected patients. The use of molecular diagnostics could reduce unnecessary or inappropriate treatment and improve identification of pathogens in resource-limited settings with high HIV burden.
authors: Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, MA 02115, USA.
authors: Lana
authors: L
authors: Dinic
authors: Oni E
authors: OE
authors: Idigbe
authors: Seema
authors: S
authors: Meloni
authors: Holly
authors: H
authors: Rawizza
authors: Patrick
authors: P
authors: Akande
authors: Geoffrey
authors: G
authors: Eisen
authors: Dan
authors: D
authors: Onwujekwe
authors: Oche
authors: O
authors: Agbaji
authors: Agatha
authors: A
authors: Ani
authors: Phyllis J
authors: PJ
authors: Kanki
mesh_terms: D000328:Adult; D019380:Anti-HIV Agents / Q000627:therapeutic use; D004269:DNA, Bacterial / Q000032:analysis; D003951:Diagnostic Errors; D005260:Female; D015658:HIV Infections / Q000150:complications* / Q000188:drug therapy; D006801:Humans; D008297:Male; D009169:Mycobacterium tuberculosis / Q000235:genetics; D057089:Pathology, Molecular / Q000379:methods; D012336:RNA, Ribosomal, 16S / Q000032:analysis*; D013183:Sputum / Q000382:microbiology*; D014376:Tuberculosis / Q000150:complications / Q000175:diagnosis* / Q000382:microbiology
chemical_list: D019380:Anti-HIV Agents; D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S