Abstract
Light-emitting diode (LED) microscopy has recently been endorsed by the World Health Organization (WHO). However, it is unclear whether LED is as accurate and cost-effective as Ziehl–Neelsen (ZN) microscopy or mercury vapour fluorescence microscopy (MVFM) in tuberculosis (TB)–HIV-co-infected subjects.
Direct and concentrated sputum smears from TB suspects were evaluated using combinations of LED microscopy, ZN microscopy and MVFM. Median reading time per slide was recorded and a cost analysis performed. Mycobacterial culture served as the reference standard.
647 sputum samples were obtained from 354 patients (88 (29.8%) were HIV-infected and 161 (26%) were culture-positive for Mycobacterium tuberculosis). Although overall sensitivity of LED compared with ZN microscopy or MVFM was similar, sensitivity of all three modalities was lower in HIV-infected patients. In the HIV-infected group, the sensitivity of LED microscopy was higher than ZN microscopy using samples that were not concentrated (46 versus 39%; p=0.25), and better than MVFM using concentrated samples (56 versus 44; p=0.5). A similar trend was seen in the CD4 count <200 cells·mL−1 subgroup. Median (interquartile range) reading time was quicker with LED compared with ZN microscopy (1.8 (1.7–1.9) versus 2.5 (2.2–2.7) min; p≤0.001). Average cost per slide read was less for LED microscopy (US$1.63) compared with ZN microscopy (US$2.10).
Among HIV–TB-co-infected patients, LED microscopy was cheaper and performed as well as ZN microscopy or MVFM independent of the staining (ZN or auramine O) or processing methods used.
Footnotes
Support Statement
This work was supported by grants from European Commission (TBSusgent; EU-FP7), EDCTP and the Canadian Institutes of Health Research (MOP-89918). J. Peter is supported by a Discovery Foundation Fellowship, the Fogarty International Clinical Research Scholars/Fellows Support Centre National Institutes of Health grant R24TW007988 and SATBAT. KD is supported by the South African NRF Research Chairs Initiative (SARChI), and an MRC Career Development Award. M. Pai is supported by a CIHR New Investigator Award. The authors have no conflicts of interest. M. Pai is a consultant to the Bill and Melinda Gates Foundation (BMGF). BMGF had no involvement in this publication.
Statement of Interest
None declared.
- Received February 8, 2011.
- Accepted April 25, 2011.
- ©ERS 2011