Clinical use of a TB Diagnostic using LAM Detection in Urine. Robin Wood, IDM, University of Cape Town

Transcription

1 Clinical use of a TB Diagnostic using LAM Detection in Urine Robin Wood, IDM, University of Cape Town

2 Declaration of Interests Statement Robin Wood, FCP (SA), D.Sc.(Med), FRS (SA). Emeritus Professor of Medicine, University of Cape Town Funding sources: National Institutes of Health South African Medical Research Council Bill & Melinda Gates Foundation No conflict of interest to declare

3 13 th March rd Sept 2016

4

5 Lipoarabinomannan, (LAM) is a lipopolysacharide mycobacterial cell wall structural component with immunogenic & immune modulatory activity

6 Alere Determine TB LAM Ag Lateral Flow Test Add 60uL urine, 25 minutes incubation at room temperature, visual inspection a) Pre-2014 LAM strip test manufacturer s reference card illustrating visual intensity grades 0 5 (b) Post new reference card illustrating visual intensity grades 0 4. The first positive band corresponds to the grade-2 band in the pior version.

7 Agreement between TB-ELISA and Determine TB-LAM LFA ELISA Overall agreement 507/ % (95%CI, ) Kappa= 0.84 (95%CI, ) WHO Review 2015 Inter- and intra-reader variability between test readers in studies, included in the review There were high degrees of agreement; 4 studies of TB diagnosis reported Kappa statistics ranging from 0.78 to studies of TB screening reported Kappa values of 0.92 to study on intra-reader agreement reported a Kappa statistic of 0.92 to 0.96.

8 Advantages of the LAM LFA Low-cost ($3.50 per test) Truly Point of Care (POC) Urine easy to obtain and easier / safer / quicker than sputum expectoration or induction Hands-on time <5 mins / results available in 25 minutes Simple read-out with no hardware requirement Rapid diagnosis in those who need quick management decisions Lack of biosafety concerns

9 Sources of LAM LFA Variability The Choice of Reference Standard Micro bacteriologically negative excluded from analysis Micro bacteriologically negative included in ref negative Micro bacteriologically negative included in ref positive Determine cut off thresholds Observer variability Urine concentration Variable storage Urine contamination Population studied

10 Receiver operator characteristic curves for urine LAM strip-test graded by two independent readers for HIVinfected patients Jonathan G. Peter et al. Eur Respir J 2012;40: A. MTB culture reference standard B. Composite reference standard

11 Diagnostic Value of Urine LAM

12 2011 Eur Respir J 2011; 38:

13 Review Conclusions 2011 The LAM urine assay was initially seen as a potentially revolutionary diagnostic for active TB. With its potential to be used as a simple point-of-care test, lack of biosafety concerns, and use of a noninvasive, convenient patient specimen, the LAM assay was fast-tracked for commercial development.this review found inadequate sensitivity to use the LAM assay for the diagnosis of active TB in unselected cohorts. The assay performs better in HIV-infected patients, especially those with severe immunodeficiency, but even in HIV-infected persons the sensitivity is suboptimal.

14 WHO policy recommendations LF-LAM should not be used for the diagnosis of TB (strong recommendation, low quality of evidence). 2 LF-LAM should not be used as a screening test for TB. (strong recommendation; low quality of evidence) 3. LF-LAM may be used to assist in the diagnosis of TB in HIV positive adult in-patients with signs and symptoms of TB (pulmonary and/or extrapulmonary) who have a CD4 cell count less than or equal to 100 cells/μl, or HIV positive patients who are seriously ill regardless of CD4 count or with unknown CD4 count (conditional recommendation; low quality of evidence).

15 2016 Objectives i.) To assess the accuracy of LF-LAM for the diagnosis of active TB disease in HIV-positive adults who have signs and symptoms suggestive of TB (TB diagnosis). ii.) To assess the accuracy of LF-LAM as a screening test for active TB disease in HIV-positive adults irrespective of signs and symptoms suggestive of TB (TB screening). The main limitations were the use of a lower quality reference standard and the small number of studies (n=12) and participants in the analyses. Cochrane Database of Systematic Reviews 2016, Issue 5. Art. No.: CD

16 Objectives i.) To assess the accuracy of LF-LAM for the diagnosis of active TB disease in HIV-positive adults who have signs and symptoms suggestive of TB (TB diagnosis). ii.) To assess the accuracy of LF-LAM as a screening test for active TB disease in HIV-positive adults irrespective of signs and symptoms suggestive of TB (TB screening). Conclusion: Lateral Flow-LAM test has low sensitivity for diagnosis or screening to detect TB but has greater utility in the seriously ill The main limitations were the use of a lower quality reference standard and the small number of studies (n=12) and participants in the analyses.. Cochrane Database of Systematic Reviews 2016, Issue 5. Art. No.: CD

17 Biological Origin of Urine LAM

18 LAM ELISA Response to TB Treatment Wood et al. BMC Infect Dis 2012

19 Mechanisms of LAM Antigenuria + HDL Wood et al. BMC Infect Dis 2012

20 Protein Concentrations in Urine of LAM positive & negative TB Cases Protein:Creatinine Ratio No evidence of significant protein leakage through renal glomerulus Wood et al. BMC Infect Dis 2012

21 Mechanisms of LAM Antigenuria + HDL Wood et al. BMC Infect Dis 2012

22 Relative Yield of Urine LAM vs Urine Xpert for HIV-Associated TB 535 Gugulethu Outpatients with Sputum Culture Positive PTB LAM Xpert Sensitivity (%) < >150 All patients CD4 cell count strata N.B. During 30 days, 4/16 (25%) of urine Xpert-positive patients died & 1/68 (1.5%) of urine Xpert-negative patients (P=0.004). Lawn, Kerkoff, Vogt, & Wood. JAIDS 2012

23 Is Urinary Lipoarabinomannan the Result of Renal Tuberculosis? Assessment of the Renal Histology in an Autopsy Cohort of Ugandan HIV-Infected Adults Cox JA, Lukande RL, Kalungi S, et al. PLoS ONE 2015;10(4): e

24 Results of Ugandan Post Mortem Study 36 PM s, 16 had TB, 13 LAM+ 7/13 LAM+ (54%) patients were not on anti-tb treatment at the time of death 8/13 LAM+ (62%) had renal TB, all renal TB LAM+ 5/13 LAM+ (38%) had disseminated TB without renal involvement 3/16 LAM- with disseminated TB without renal involvement

25 Conclusions of Post Mortem Study: 1. Renal TB infection explained LAM-positivity in the majority of patients. 2. Some patients with disseminated TB without renal involvement were also diagnosed with LAM. 3. This suggests that other mechanisms that lead to urinary LAM-positivity may exist in a minority of patients. However: Could small foci of renal TB have been missed? Was prostatic, urethral, bladder and genital TB excluded? Post-mortem collection of urine may have affected ELISA sensitivity.

26 Mechanisms of LAM Antigenuria + HDL 4 fmol? Wood et al. BMC Infect Dis 2012

27 Prognostic Value of Urine LAM

28 Figure 3 The sensitivities (%) with 95% confidence intervals of urine-based (n = 81) and sputum-based (n = 86) diagnostic tests for tuberculosis (TB). Data are shown stratified according to haemoglobin. BMC Med Oct 29;11:231

29 Figure 3 The sensitivities (%) with 95% confidence intervals of urine-based (n = 81) and sputum-based (n = 86) diagnostic tests for tuberculosis (TB). Data are shown stratified according to vital status at 90 days. BMC Med Oct 29;11:231

30 Detection of lipoarabinomannan (LAM) in urine is an independent predictor of mortality risk in patients receiving treatment for HIVassociated tuberculosis in sub-saharan Africa: a systematic review and meta-analysis Fig. 3 Forest plot showing adjusted odds ratio of mortality in urinary lipoarabinomannan (LAM)-positive tuberculosis (TB) cases compared to urinary LAM-negative TB cases, stratified by overall mortality in TB cases. Gupta-Wright et al. BMC Medicine (2016) 14:53

31 Mortality Benefit of POC Urine LAM Testing 2,659 Hospitalized TB suspects 4 countries Tanzania, South Africa, Zambia & Zimbabwe Randomized to either: A. Routine - Sputum microscopy, MTB Culture, Xpert or B. Routine - & POC urine LAM Results Endpoints A. Routine Care B. Routine & LAM P value Starting TB Rx 47% 52% Days to Rx 1 (1-3) Empiric Rx 70% 48% Total 8 week mortality 1 (ahr) 0.81 (ahr) CD4 <50 mortality 1 (ahr) 0.68 (ahr) <0.001 JG Peter et al. Lancet Mar 19;387(10024):

32 Rapid urine-based screening for TB to reduce AIDSrelated mortality in hospitalised patients in Africa Post-mortem studies show that TB is the cause of up to 2/3 of adult HIV/AIDS-related deaths recorded in health facilities in sub-saharan Africa. However, around 50% of these TB cases are undiagnosed at the time of death, highlighting the urgent need for new diagnostic approaches. Background studies conducted in Cape Town by Stephen Lawn show that a large majority of TB cases can be rapidly diagnosed from a urine sample within the first 24 hours of acute hospital admission, using a combination of two techniques: Determine TBLAM lateral-flow urine test and Xpert MTB/RIF testing of concentrated urine. The three-year Screening for Tuberculosis to Reduce AIDS-Related Mortality in Hospitalized Patients in Africa (STAMP) study, started in 2015, is a randomised controlled trial to assess the clinical outcomes of standard sputum-based testing with Xpert MTB/RIF plus additional urine-based screening, compared with the standard screening alone. Funded by a UK Medical Research Council, Department for International Development and Wellcome Trust Global Clinical Trials Scheme grant award of 2.1 million over three years, the trial is underway in both Malawi and KwaZulu Natal, South Africa. Principal Investigator: Stephen D. Lawn

33 Final Conclusions Urine LFA for LAM was developed as a test for active PTB but the current format performs as a test for renal tuberculosis Renal disease occurs in the sickest TB/HIV co-infected patients & is strongly associated with very poor prognosis There is rationale for routine urine LAM testing in management of sick hospitalised HIV-infected patients

34 Professor Stephen Lawn Memorial Fund