Feasibility of a Lateral Flow Urine Lipoarabinomannan (LAM) Test for Diagnosis of Tuberculosis

• Sensitivity of the lateral-flow urine LAM assay (LF-LAM) [ Time Frame: One year ] [ Designated as safety issue: No ]
  • Conventional TB tests (mycobacterial blood & sputum culture) will be the reference standard used to calculate sensitivity of the LF-LAM test
  • Sensitivity is defined as TP/(TP+FN), or the number of true positives over (the number of true positives + the number of false negatives)
  • "true positive" = a positive LF-LAM result in a patient also having ≥1 culture positive for M. tuberculosis
  • "false negative" = a negative LF-LAM result in a patient also having ≥1 culture positive for M. tuberculosis
  
  
• Failure rate of the lateral-flow urine LAM assay [ Time Frame: One year ] [ Designated as safety issue: No ]
  Failure rate expressed as the proportion of lateral flow urine LAM tests that require repeating due to an unevaluable initial result
  
  
• Inter-reader variability of the lateral-flow urine LAM assay [ Time Frame: One year ] [ Designated as safety issue: No ]
  Expressed as the percent agreement
  
  
• Specificity of the lateral-flow urine LAM assay (LF-LAM) [ Time Frame: One year ] [ Designated as safety issue: No ]
  • Conventional TB tests (blood & sputum culture) will be the reference standard used to calculate specificity (Sp) of the LF-LAM
  • Sp=TN/(TN+FP), or #true negatives / (#true negatives + #false positives)
  • "true negative" = negative LF-LAM in "Not TB" patient
  • "false positive" = positive LF-LAM in "Not TB" patient

  • "Not TB" = meets all criteria below

    • no sputum/blood culture positive for MTB
    • no smear microscopy positive for acid-fast bacilli
    • no granulomas/caseous necrosis on histopathology
    • no clinical response to TB treatment
    • a plausible alternative diagnosis
  
  

• Sensitivity of the ELISA-based urine LAM test [ Time Frame: One year ] [ Designated as safety issue: No ]
  • Conventional TB tests (mycobacterial blood & sputum culture) will be the reference standard used to calculate sensitivity of the ELISA LAM test
  • Sensitivity is defined as TP/(TP+FN), or the number of true positives over (the number of true positives + the number of false negatives)
  • "true positive" = a positive ELISA LAM result in a patient also having ≥1 culture positive for M. tuberculosis
  • "false negative" = a negative ELISA LAM result in a patient also having ≥1 culture positive for M. tuberculosis
  
  
• Diagnostic yield (expressed as number of TB cases detected) of various diagnostic strategies (see description) [ Time Frame: One year ] [ Designated as safety issue: No ]
  Diagnostic yield will be measured for strategies including a) lateral flow urine LAM testing plus sputum smear microscopy; b) ELISA urine LAM testing plus sputum smear microscopy; c) sputum smear microscopy plus sputum culture; d) sputum culture plus mycobacterial blood culture.
  
  
• Time to diagnosis (expressed in days) of various diagnostic strategies (see description) [ Time Frame: One year ] [ Designated as safety issue: No ]
  Time to diagnosis will be measured for strategies including a) lateral flow urine LAM testing plus sputum smear microscopy; b) ELISA urine LAM testing plus sputum smear microscopy; c) sputum smear microscopy plus sputum culture; d) sputum culture plus mycobacterial blood culture.
  
  
• Accuracy, efficiency, costs, and cost-effectiveness of various combinations of TB diagnostic tests [ Time Frame: One year ] [ Designated as safety issue: No ]
  TB diagnostic tests to be included in this analysis: sputum smear microscopy, sputum culture, mycobacterial blood culture, chest X-ray, lateral-flow urine LAM testing, ELISA urine LAM testing, and Xpert MTB/Rif.
  
  
• Satisfaction of lateral-flow urine LAM test operators [ Time Frame: One year ] [ Designated as safety issue: No ]
  Based on questionnaire assessment
  
  
• Specificity (Sp) of the ELISA-based urine LAM test [ Time Frame: One year ] [ Designated as safety issue: No ]
  • Conventional TB tests (blood & sputum culture) will be the reference standard used to calculate Sp of ELISA LAM
  • Sp=TN/(TN+FP), or #true negatives / (#true negatives + #false positives)
  • "true negative" = negative ELISA LAM in "Not TB" patient
  • "false positive" = positive ELISA LAM in "Not TB" patient

  • "Not TB" = meets all criteria below

    • no sputum/blood culture positive for MTB
    • no smear microscopy positive for acid-fast bacilli
    • no granulomas/caseous necrosis on histopathology
    • no clinical response to TB treatment
    • a plausible alternative diagnosis
  
  

Device: Alere "Determine" lateral-flow urine lipoarabinomannan assay

lateral-flow (point-of-care) urine test to detect the lipoarabinomannan (LAM) component of the M. tuberculosis antigen in the urine of TB suspects, in vitro.

Manufacturer: Alere

Other Name: Determine lateral-flow urine LAM TB test
Device: Alere "Clearview" ELISA urine LAM assay

ELISA-based urine test to detect the lipoarabinomannan component of the M. tuberculosis antigen in the urine of TB suspects, in vitro.

Manufacturer: Alere.

Other Name: Clearview ELISA urine LAM TB test

Background: Tuberculosis (TB) incidence and mortality have increased dramatically as a result of the HIV epidemic. In parts of sub-Saharan Africa, TB is the leading cause of death among HIV-infected patients and approximately 50% of TB patients are HIV co-infected. Early treatment of TB is hindered by the lack of rapid, accurate diagnostic modalities that can be applied in resource-constrained settings. Mycobacterial culture is the laboratory standard for diagnosis of active TB, but it is costly, requires access to specialized laboratories, and takes weeks to provide results. Sputum smear microscopy detects less than half of HIV-infected TB cases in many settings. The Global Plan to Stop TB has prioritized the development of simple, accurate, inexpensive tests for TB case detection in HIV-positive individuals.

LAM: As a strategy for rapid TB diagnosis, the detection of Mycobacterium tuberculosis antigens has been explored over several decades. Lipoarabinomannan (LAM), a glycolipid component of the outer cell wall of mycobacteria, is an attractive diagnostic target for several reasons: it is heat-stable; cleared by the kidney; detectable in urine; and as a bacterial product, has the theoretical potential to discriminate active TB from latent TB infection independent of human immune responses. A urine test could facilitate TB diagnosis in patients in whom sputum is uninformative or not obtainable, and lacks the infection-control risks associated with sputum production or blood collection. Urine LAM detection may be amenable to simple, rapid, inexpensive point-of-care platforms.

This is a prospective study to evaluate the accuracy, diagnostic yield, operational performance, and time to diagnosis of a novel lateral-flow urine LAM test in detecting tuberculosis in HIV-infected adults. HIV-positive adults suspected to have TB will be enrolled after providing informed consent. Urine will be obtained for testing using the novel lateral flow urine LAM assay and an existing ELISA-based urine LAM assay. Conventional microbiological tests for TB and chest x-rays will also be performed. These tests will be performed on all participants enrolled (target sample size = 500).

A secondary study objective is to determine the accuracy, efficiency, costs, and cost-effectiveness of various combinations of TB diagnostic tests, including the novel Xpert MTB/Rif test. The Xpert MTB/Rif test will be performed on a subset of participants (approximately 200 participants out of the total of 500 participants we expect to enroll for the LAM component of the study.)