A Controlled Study of Tuberculosis Diagnosis in HIV-Infected and Uninfected Children in Peru

Abstract

Background: Diagnosing tuberculosis in children is challenging because specimens are difficult to obtain and contain low tuberculosis concentrations, especially with HIV-coinfection. Few studies included well-controls so test specificities are poorly defined. We studied tuberculosis diagnosis in 525 children with and without HIV-infection.

Methods and findings: 'Cases' were children with suspected pulmonary tuberculosis (n = 209 HIV-negative; n = 81 HIV-positive) and asymptomatic 'well-control' children (n = 200 HIV-negative; n = 35 HIV-positive). Specimens (n = 2422) were gastric aspirates, nasopharyngeal aspirates and stools analyzed by a total of 9688 tests. All specimens were tested with an in-house hemi-nested IS6110 PCR that took <24 hours. False-positive PCR in well-controls were more frequent in HIV-infection (P≤0.01): 17% (6/35) HIV-positive well-controls versus 5.5% (11/200) HIV-negative well-controls; caused by 6.7% (7/104) versus 1.8% (11/599) of their specimens, respectively. 6.7% (116/1719) specimens from 25% (72/290) cases were PCR-positive, similar (P>0.2) for HIV-positive versus HIV-negative cases. All specimens were also tested with auramine acid-fast microscopy, microscopic-observation drug-susceptibility (MODS) liquid culture, and Lowenstein-Jensen solid culture that took ≤6 weeks and had 100% specificity (all 2112 tests on 704 specimens from 235 well-controls were negative). Microscopy-positivity was rare (0.21%, 5/2422 specimens) and all microscopy-positive specimens were culture-positive. Culture-positivity was less frequent (P≤0.01) in HIV-infection: 1.2% (1/81) HIV-positive cases versus 11% (22/209) HIV-negative cases; caused by 0.42% (2/481) versus 4.7% (58/1235) of their specimens, respectively.

Conclusions: In HIV-positive children with suspected tuberculosis, diagnostic yield was so low that 1458 microscopy and culture tests were done per case confirmed and even in children with culture-proven tuberculosis most tests and specimens were false-negative; whereas PCR was so prone to false-positives that PCR-positivity was as likely in specimens from well-controls as suspected-tuberculosis cases. This demonstrates the importance of control participants in diagnostic test evaluation and that even extensive laboratory testing only rarely contributed to the care of children with suspected TB.

Trial registration: This study did not meet Peruvian and some other international criteria for a clinical trial but was registered with the ClinicalTrials.gov registry: ClinicalTrials.gov NCT00054769.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1. Study flow chart.

Fig 2. Tuberculosis (TB) test results for specimens from HIV-positive and HIV-negative case and well-control children.

Data are analysed by assessment of probability of TB disease indicated by the Stegen-Toledo (ST) clinical score (see Methods). (A) TB PCR results. (B) Microscopy and culture test results: auramine microscopy, microscopic-observation drug-susceptibility (MODS) liquid culture, and Lowenstein Jensen solid culture.

Fig 3. Tuberculosis (TB) microscopy and culture test results for specimens from the 23 cases with culture-positive TB.

All subjects had two specimens of each type analyzed for TB by the methods shown. The graph shows the proportion (and the data table the number) of patients who had positive results in (A.) at least one of their two specimens and (B.) who had positive results in the first specimen of their two specimens, with separate bars indicating results for stool, nasopharyngeal aspirate (NPA) or gastric aspirate specimens tested only by auramine microscopy (smear), Lowenstein-Jensen (LJ) solid culture, or microscopic-observation drug-susceptibility (MODS) liquid culture [e.g. the first bar demonstrates that all 23 cases would have been diagnosed if only (1.) LJ and MODS culture had been performed (i.e. without microscopy) on (A.) duplicate gastric aspirate specimens].

Fig 4. The number of tuberculosis (TB) microscopy and culture tests done for each case confirmed.

A. All cases had duplicate stool, nasopharyngeal aspirate (NPA) and gastric aspirate specimens tested for tuberculosis (TB) by auramine microscopy (smear), Lowenstein-Jensen (LJ) solid culture, and microscopic-observation drug-susceptibility (MODS) liquid culture [e.g. the left-most gray bar indicates that in this study 1458 tests (1. smear, LJ and MODS) were done (on A. stool, NPA and gastric aspirates) per HIV-positive case diagnosed; whereas the right-most black bar indicates that in this study if only (2.) smear and MODS testing had been done on only (B.) duplicate gastric aspirates then 42 tests would have been done per HIV-negative case diagnosed].