Sensitivity of direct versus concentrated sputum smear microscopy in HIV-infected patients suspected of having pulmonary tuberculosis.
BACKGROUND
Sputum concentration increases the sensitivity of smear microscopy for the diagnosis of tuberculosis (TB), but few studies have investigated this method in human immunodeficiency virus (HIV)-infected individuals.


METHODS
We performed a prospective, blinded evaluation of direct and concentrated Ziehl-Neelsen smear microscopy on a single early-morning sputum sample in HIV-infected patients with > 2 weeks of cough hospitalized in Kampala, Uganda. Direct and concentrated smear results were compared with results of Lowenstein-Jensen culture.


RESULTS
Of 279 participants, 170 (61%) had culture-confirmed TB. The sensitivity of direct and concentrated smear microscopy was not significantly different (51% vs. 52%, difference 1%, 95% confidence interval (CI): [-7%, 10%], p = 0.88). However, when results of both direct and concentrated smears were considered together, sensitivity was significantly increased compared with either method alone (64%, 95% CI: [56%, 72%], p < 0.01 for both comparisons) and was similar to that of direct smear results from consecutive (spot and early-morning) specimens (64% vs. 63%, difference 1%, 95% CI: [-6%, 8%], p = 0.85). Among 109 patients with negative cultures, one had a positive direct smear and 12 had positive concentrated smears (specificity 99% vs. 89%, difference 10%, 95% CI: [2%, 18%], p = 0.003). Of these 13 patients, 5 (38%) had improved on TB therapy after two months.


CONCLUSIONS
Sputum concentration did not increase the sensitivity of light microscopy for TB diagnosis in this HIV-infected population. Given the resource requirements for sputum concentration, additional studies using maximal blinding, high-quality direct microscopy, and a rigorous gold standard should be conducted before universally recommending this technique.
Division of Pulmonary and Critical Care Medicine, University of California, San Francisco, CA, USA. acattamanchi@medsfgh.ucsf.edu
Adithya
A
Cattamanchi
David W
DW
Dowdy
J Lucian
JL
Davis
William
W
Worodria
Samuel
S
Yoo
Moses
M
Joloba
John
J
Matovu
Philip C
PC
Hopewell
Laurence
L
Huang
D000328:Adult; D001431:Bacteriological Techniques; D005260:Female; D015658:HIV Infections / Q000150:complications* / Q000382:microbiology; D006801:Humans; D008297:Male; D008853:Microscopy; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification*; D011446:Prospective Studies; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013183:Sputum / Q000382:microbiology*; D018709:Statistics, Nonparametric; D014397:Tuberculosis, Pulmonary / Q000150:complications / Q000175:diagnosis*; D014454:Uganda