Sensitivity and specificity of fluorescence microscopy for diagnosing pulmonary tuberculosis in a high HIV prevalence setting

Int J Tuberc Lung Dis. 2009 Sep;13(9):1130-6.


Setting: Mulago Hospital, Kampala, Uganda.

Objective: To evaluate the diagnostic performance of fluorescence microscopy (FM) for diagnosing pulmonary tuberculosis (TB) in a high human immunodeficiency virus (HIV) prevalence setting.

Design: Consecutive in-patients with cough for >2 weeks submitted two sputum specimens for smear microscopy. Smears were examined by conventional light microscopy (CM) and FM. The performance of the two methods was compared using mycobacterial culture as a reference standard.

Results: A total of 426 patients (82% HIV-infected) were evaluated. FM identified 11% more smear-positive patients than CM (49% vs. 38%, P < 0.001). However, positive FM results were less likely than positive CM results to be confirmed by culture when smears were read as either 'scanty' (54% vs. 90%, P < 0.001) or 1+ (82% vs. 91%, P = 0.02). Compared to CM, the sensitivity of FM was higher (72% vs. 64%, P = 0.005), and the specificity lower (81% vs. 96%, P < 0.001). In receiver operating characteristic analysis, maximum area under the curve for FM was obtained at a threshold of >4 acid-fast bacilli/100 fields (sensitivity 68%, specificity 90%).

Conclusion: Although FM increases the sensitivity of sputum smear microscopy, additional data on FM specificity and on the clinical consequences associated with false-positive FM results are needed to guide implementation of this technology in high HIV prevalence settings.

Publication types

  • Comparative Study
  • Evaluation Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Bacteriological Techniques* / standards
  • Colony Count, Microbial
  • Cough / microbiology
  • False Positive Reactions
  • Female
  • HIV Infections / complications*
  • HIV Infections / epidemiology
  • Humans
  • Male
  • Microscopy, Fluorescence* / standards
  • Mycobacterium tuberculosis / isolation & purification*
  • Predictive Value of Tests
  • Prevalence
  • Prospective Studies
  • ROC Curve
  • Reference Standards
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Sputum / microbiology
  • Staining and Labeling* / standards
  • Tuberculosis, Pulmonary / diagnosis*
  • Tuberculosis, Pulmonary / epidemiology
  • Tuberculosis, Pulmonary / microbiology
  • Uganda / epidemiology