Jonathan G. Peter

Diagnostic accuracy of a urine lipoarabinomannan strip-test for TB detection in HIV-infected hospitalised patients

Lack of point-of-care tests for tuberculosis (TB) result in diagnostic delay, and increased mortality and healthcare-related costs. The urine DetermineTM TB-LAM point-of-care strip-test was evaluated in 335 prospectively-recruited hospitalised patients with suspected TB-HIV co-infection (group 1) and from 88 HIV-infected hospitalised patients with non-TB diagnoses (group 2). Cut-off point-specific analyses were performed using: 1) a microbiological reference standard (culture positive versus negative); and 2) a composite reference standard (exclusion of patients with clinical-TB from the culture-negative group). Using the microbiological reference and the manufacturer-recommended grade-1 cut-off point, LAM sensitivity and specificity was 66% (95% CI 57–74%). By contrast, using the composite reference sensitivity was 60% (95% CI 53–67%) and specificity improved to 96% (95% CI 89–100%) (p=0.001). The same pattern was seen when the grade-2 cut-off point was used (specificity 75% versus 96%; p=0.01). In group two patients specificity was poor using the grade-1 cut-off point, but improved significantly when the grade-2 cut-off point was used (90% versus 99%; p=0.009). The grade-2 cut-off point also offered superior inter-reader reliability (p=0.002). Sensitivity was highest in those with a CD4 <200 cells per mL. LAM combined with smear-microscopy was able to rule-in TB in 71% of Mycobacterium tuberculosis culture-positive patients. This preliminary study indicates that the LAM strip-test may be a potentially useful rapid rule-in test for TB in hospitalised patients with advanced immunosuppression. The grade 2, but not the manufacturer-recommended grade 1 cut-off point, offered superior rule-in utility and inter-reader reliability. Larger studies to evaluate cut-off points and diagnostic accuracy are urgently required.

Determine TB-LAM lateral flow urine antigen assay for HIV-associated tuberculosis: recommendations on the design and reporting of clinical studies.

Detection of the Mycobacterium tuberculosis cell wall antigen lipoarabinomannan (LAM) in urine permits diagnoses of tuberculosis (TB) to be made in HIV-infected patients with advanced immunodeficiency. This can be achieved at the point-of-care within just 30 minutes using the Determine TB-LAM, which is a commercially available, lateral-flow urine ‘strip test’ assay. The assay has been shown to have useful diagnostic accuracy in patients enrolling in antiretroviral treatment services or in HIV-infected patients requiring admission to hospital medical wards in sub-Saharan Africa. Such patients have high mortality risk and have most to gain from rapid diagnosis of TB and immediate initiation of treatment. However, few studies using this assay have yet been reported and many questions remain concerning the correct use of the assay, interpretation of results, the role of the assay as an add-on test within existing diagnostic algorithms and the types of further studies needed. In this paper we address a series of questions with the aim of informing the design, conduct and interpretation of future studies. Specifically, we clarify which clinical populations are most likely to derive benefit from use of this assay and how patients enrolled in such studies might best be characterised. We describe the importance of employing a rigorous microbiological diagnostic reference standard in studies of diagnostic accuracy and discuss issues surrounding the specificity of the assay in different geographical areas and potential cross-reactivity with non-tuberculous mycobacteria and other organisms. We highlight the importance of careful procedures for urine collection and storage and the critical issue of how to read and interpret the test strips. Finally, we consider how the assay could be used in combination with other assays and outline the types of studies that are required to build the evidence base concerning its use.

The Diagnostic Accuracy of Urine-Based Xpert MTB/RIF in HIV-Infected Hospitalized Patients Who Are Smear-Negative or Sputum Scarce

Background Hospitals in sub-Saharan Africa are inundated with HIV-infected patients and tuberculosis (TB) is the commonest opportunistic infection in this sub-group. Up to one third of TB-HIV co-infected patients fail to produce a sputum sample (sputum scarce) and diagnosis is thus often delayed or missed. We investigated the sensitivity of urine-based methods (Xpert MTB/RIF, LAM strip test and LAM ELISA) in such patients. Methodology/Principal Findings 281 HIV-infected hospitalised patients with clinically suspected TB provided a spot urine sample. The reference standard was culture positivity for Mycobacterium tuberculosis on ≥1 sputum or extra-pulmonary sample. MTB/RIF was performed using 1 ml of both unprocessed and, when possible, concentrated urine. Each unconcentrated urine sample was also tested using the Clearview LAM ELISA and Alere LAM strip test. 42% (116/242) of patients had culture-proven TB. 18% (20/54) were sputum scarce. In sputum-scarce patients, the sensitivity of urine MTB/RIF and LAM ELISA was 40% (95%CI: 22–61) and 60% (95%CI: 39–78), respectively. Urine MTB/RIF specificity was 98% (95%CI: 95–100). Combined sensitivity of urine LAM ELISA and MTB/RIF was better than MTB/RIF alone [MTB/RIF and LAM: 70% (95%CI: 48–85) vs. MTB/RIF: 40% (95%CI: 22–61), p = 0.03]. Significant predictors of urine MTB/RIF positivity were CD4<50 cells/ml (p = 0.001), elevated protein-to-creatinine ratio (p<0.001) and LAM ELISA positivity (p<0.001). Urine centrifugation and pelleting significantly increased the sensitivity of MTB/RIF over unprocessed urine in paired samples [42% (95%CI: 26–58) vs. 8% (95%CI: 0–16), p<0.001]. Urine MTB/RIF-generated CT values correlated poorly with markers of bacillary burden (smear grade and time-to-positivity). Conclusions/Significance This preliminary study indicates that urine-based MTB/RIF, alone or in combination with LAM antigen detection, may potentially aid the diagnosis of TB in HIV-infected patients with advanced immunosuppression when sputum-based diagnosis is not possible. Concentration of urine prior to MTB/RIF-testing significantly improves sensitivity.

Can point-of-care urine LAM strip testing for tuberculosis add value to clinical decision making in hospitalised HIV-infected persons?

Background The urine lipoarabinomannan (LAM) strip-test (Determine®-TB) can rapidly rule-in TB in HIV-infected persons with advanced immunosuppression. However, given high rates of empiric treatment amongst hospitalised patients in high-burden settings (∼50%) it is unclear whether LAM can add any value to clinical decision making, or identify a subset of patients with unfavourable outcomes that would otherwise have been missed by empiric treatment. Methods 281 HIV-infected hospitalised patients with suspected TB received urine LAM strip testing, and were categorised as definite (culture-positive), probable-, or non-TB. Both the proportion and morbidity of TB cases identified by LAM testing, early empiric treatment (initiated prior to test result availability) and a set of clinical predictors were compared across groups. Results 187/281 patients had either definite- (n = 116) or probable-TB (n = 71). As a rule-in test for definite and probable-TB, LAM identified a similar proportion of TB cases compared to early empiric treatment (85/187 vs. 93/187, p = 0.4), but a greater proportion than classified by a set of clinical predictors alone (19/187; p<0.001). Thirty-nine of the 187 (21%) LAM-positive patients who had either definite- or probable-TB were missed by early empiric treatment, and of these 25/39 (64%) would also have been missed by smear microscopy. Thus, 25/187 (8%) of definite- or probable-TB patients with otherwise delayed initiation of TB treatment could be detected by the LAM strip test. LAM-positive patients missed by early empiric treatment had a lower median CD4 count (p = 0.008), a higher median illness severity score (p = 0.001) and increased urea levels (p = 0.002) compared to LAM-negative patients given early empiric treatment. Conclusions LAM strip testing outperformed TB diagnosis based on clinical criteria but in day-to-day practice identified a similar proportion of patients compared to early empiric treatment. However, compared to empiric treatment, LAM identified a different subset of patients with more advanced immunosuppression and greater disease severity.

Sensitivity of C-Tb: a novel RD-1-specific skin test for the diagnosis of tuberculosis infection

C-Tb, a novel Mycobacterium tuberculosis and 6-kDa early secretory antigenic target/10-kDa culture filtrate protein (ESAT-6/CFP-10)-specific skin test, has high specificity in bacille Calmette–Guerin-vaccinated healthy controls. However, the sensitivity of C-Tb has hitherto not been determined. The objective was to determine the sensitivity of C-Tb in patients with active tuberculosis (TB) in comparison with the tuberculin skin test (TST) and QuantiFERON-TB Gold In-Tube (QFT-GIT). C-Tb and TST were randomly administered in a double-blinded fashion to one or the other forearm in 253 patients with active TB with or without HIV co-infection. QFT-GIT testing was performed prior to skin testing. Using a receiver operating characteristic curve-derived cut-point of 5 mm, C-Tb sensitivity was similar to QFT-GIT (73.9 (95% CI 67.8–79.3) versus 75.1 (95% CI 69.3–80.2)), and similar in HIV-infected and HIV-uninfected patients (76.7 (95% CI 69.0–83.3) versus 69.5 (95% CI 59.2–78.5)). However, sensitivity was significantly diminished in HIV-infected patients with CD4 counts <100 cells·mm–3. C-Tb and QFT-GIT combined had significantly higher sensitivity than C-Tb alone (p<0.0001). C-Tb was safe with no significant adverse events. The 5 mm cut-point corresponded to that found in the previously published specificity study (TESEC-04). C-Tb has similar sensitivity compared with QFT-GIT for the diagnosis of M. tuberculosis infection. Sensitivity was reduced only in HIV-infected patients with severe immunosuppression. Further studies in different settings are required to validate the proposed 5 mm cut-point. C-Tb has similar sensitivity compared with QFT-GIT for the diagnosis of M. tuberculosis infection http://ow.ly/TtFf6

Sputum induction to aid diagnosis of smear-negative or sputum-scarce tuberculosis in adults in HIV-endemic settings

Sputum induction can aid tuberculosis (TB) diagnosis, but adult data from HIV-endemic environments are limited, and it is unclear how performance varies depending on the clinical context (in-patient versus outpatient), HIV status and whether patients are smear-negative or sputum-scarce. 696 adults with suspected smear-negative or sputum-scarce TB from Cape Town (South Africa) were referred for routine sputum induction. Liquid culture for Mycobacterium tuberculosis served as the reference standard. 82% (573 out of 696) of patients provided a specimen ≥1 mL, 83% (231 out of 278) of which were of adequate quality. 15% (96 out of 652) of sputum induction specimens were culture-positive, and this yield was higher among inpatients versus outpatients (17% (71 out of 408) versus 10% (25 out of 244), p=0.01) and HIV-infected versus uninfected patients (17% (51 out of 294) versus 9% (16 out of 173), p=0.02), but similar for CD4 (>200 versus ≤200 cells·&mgr;L−1) and patient (smear-negative versus sputum-scarce) subcategories. Overall sensitivity (95% CI) of smear-microscopy was 49% (39–59%), higher among in-patients versus outpatients (55% (43–67%) versus 32% (14–50%), p=0.05), but unaffected by HIV co-infection, CD4 count or patient type. 29% (203 out of 696) of patients commenced anti-TB treatment and sputum induction offered microbiological confirmation and susceptibility testing in only 47% (96 out of 203). Under programmatic conditions in an HIV-endemic environment although the yield of culture was approximately two-fold higher amongst HIV-infected patients and inpatients, a fifth of all patients were unable to provide a specimen following sputum induction. Same-day microbiological diagnosis was only possible in ∼50% of patients. TB culture yield is approximately two-fold higher among HIV-infected patients and in patients http://ow.ly/qeJrx

Feasibility and diagnostic utility of antigen-specific interferon-γ responses for rapid immunodiagnosis of tuberculosis using induced sputum.

Background The diagnosis of smear-negative or sputum-scarce tuberculosis (TB) is problematic as culture takes several weeks and representative biological samples are difficult to obtain. RD-1 antigen-specific interferon-γ release assays (IGRAs) are sensitive and specific blood-based tests for the diagnosis of M. tuberculosis infection. The feasibility and diagnostic utility of this rapid immunodiagnostic assay, using cells from induced sputum, is unknown. Methodology/Principal Findings Cells isolated from induced sputum were co-cultured with ESAT-6 and CFP-10 antigens using a standardized enzyme-linked immunospot (ELISPOT) assay (T-SPOT®.TB) in 101 consecutively recruited TB suspects or non-TB controls. An optimization phase using 28 samples was followed by a validation phase using samples from 73 participants (20 with definite or probable TB, and 48 with non-TB). Despite optimization of sputum processing 65/73 (89%) of the IGRAs in the validation phase were inconclusive. 44/73 (60%) tests failed due to sputum induction-related factors [sputum induction-related adverse events (n = 5), inadequate sputum volume (n = 8), non-homogenisable sputum (n = 7), and insufficient numbers of cells to perform the assay (n = 24)], whilst 20/73 (27%) tests failed due T-SPOT®.TB assay-related factors [excessive debris precluding reading of spots in the ELISPOT well (n = 6), failure of the positive control (n = 11), or high spot count in the negative control (n = 3)]. Only 8/73 (11%) of the available samples could therefore be correctly categorized (7 definite or probable TB, and 1 non-TB patient). Thus, 13/20 (65%) of the definite or probable TB cases remained undiagnosed. Conclusions/Significance Rapid immunodiagnosis of pulmonary TB by antigen-specific IFN-γ ELISPOT responses, using cells from induced sputum, is possible. However, the test, in its current ELISPOT format, is not clinically useful because the majority of the assays are inconclusive.

Severe Delayed Cutaneous and Systemic Reactions to Drugs: A Global Perspective on the Science and Art of Current Practice

Most immune-mediated adverse drug reactions (IM-ADRs) involve the skin, and many have additional systemic features. Severe cutaneous adverse drug reactions (SCARs) are an uncommon, potentially life-threatening, and challenging subgroup of IM-ADRs with diverse clinical phenotypes, mechanisms, and offending drugs. T-cell-mediated immunopathology is central to these severe delayed reactions, but effector cells and cytokines differ by clinical phenotype. Strong HLA-gene associations have been elucidated for specific drug-SCAR IM-ADRs such as Stevens-Johnson syndrome/toxic epidermal necrolysis, although the mechanisms by which carriage of a specific HLA allele is necessary but not sufficient for the development of many IM-ADRs is still being defined. SCAR management is complicated by substantial short- and long-term morbidity/mortality and the potential need to treat ongoing comorbid disease with related medications. Multidisciplinary specialist teams at experienced units should care for patients. In the setting of SCAR, patient outcomes as well as preventive, diagnostic, treatment, and management approaches are often not generalizable, but rather context specific, driven by population HLA-genetics, the pharmacology and genetic risk factors of the implicated drug, severity of underlying comorbid disease necessitating ongoing treatments, and cost considerations. In this review, we update the basic and clinical science of SCAR diagnosis and management.

Effect of new tuberculosis diagnostic technologies on community-based intensified case finding: a multicentre randomised controlled trial

BACKGROUND Inadequate case detection results in high levels of undiagnosed tuberculosis in sub-Saharan Africa. Data for the effect of new diagnostic tools when used for community-based intensified case finding are not available, so we investigated whether the use of sputum Xpert-MTB/RIF and the Determine TB LAM urine test in two African communities could be effective. METHODS In a pragmatic, randomised, parallel-group trial with individual randomisation stratified by country, we compared sputum Xpert-MTB/RIF, and if HIV-infected, the Determine TB LAM urine test (novel diagnostic group), with laboratory-based sputum smear microscopy (routine diagnostic group) for intensified case finding in communities with high tuberculosis and HIV prevalence in Cape Town, South Africa, and Harare, Zimbabwe. Participants were randomly assigned (1:1) to these groups with computer-generated allocation lists, using culture as the reference standard. In Cape Town, participants were randomised and tested at an Xpert-equipped mobile van, while in Harare, participants were driven to a local clinic where the same diagnostic tests were done. The primary endpoint was the proportion of culture-positive tuberculosis cases initiating tuberculosis treatment in each study group at 60 days. This trial is registered at ClinicalTrials.gov, number NCT01990274. FINDINGS Between Oct 18, 2013, and March 31, 2015, 2261 individuals were screened and 875 (39%) of these met the criteria for diagnostic testing. 439 participants were randomly assigned to the novel group and 436 to the routine group. 74 (9%) of 875 participants had confirmed tuberculosis. If late culture-based treatment initiation was excluded, more patients with culture-positive tuberculosis were initiated on treatment in the novel group at 60 days (36 [86%] of 42 in the novel group vs 18 [56%] of 32 in the routine group). Thus the difference in the proportion initiating treatment between groups was 29% (95% CI 9-50, p=0·0047) and 53% more patients initiated therapy in the novel diagnostic group than in the routine diagnostic group. One culture-positive patient was treated based only on a positive LAM test. INTERPRETATION Compared with traditional tools, Xpert-MTB/RIF for community-based intensified case finding in HIV and tuberculosis-endemic settings increased the proportion of patients initiating treatment. By contrast, urine LAM testing was not found to be useful for intensive case finding in this setting. FUNDING European and Developing Countries Clinical Trials Partnership and South African Medical Research Council.

Twelve-month outcomes of patients admitted to the acute general medical service at Groote Schuur Hospital

OBJECTIVES Hospitalisation for medical illness has ongoing impact on individuals, healthcare services and society beyond discharge. This studys objective was to determine the 12-month mortality and functional outcomes of patients admitted to the acute medical service at Groote Schuur Hospital (GSH). METHODS Follow-up, using the hospital records system and provincial death registry, together with telephonic interviews or home visits, was attempted for 465 medical inpatients admitted to GSH between 14 September and 16 November 2009. Functional outcomes were assessed using the Katz activities of daily living (ADL) score and Barthel index (BI). Outcome measures. The major study outcomes included: 12-month mortality (overall and unexpected), changes in functional status and pre- and post-admission employment rates. RESULTS Inpatient mortality was 11%. At 12-month follow-up, 35% (145/415) were deceased and 30% (125/415) could not be traced; 38% (55/145) of deaths were considered expected and unexpected mortality was associated with age >40 years (p=0.02) and an admission urea >7.0 mmol/l (p=0.004). Katz ADL deteriorated in 15% (21/143) of interviewed patients and was associated with age >50 years (p=0.005); 23% (33/143) had improved Katz ADL associated with admission human immunodeficiency virus (HIV) (p=0.01), tuberculosis (TB) infection (p=0.05) and sepsis (p=0.02). Employment rates declined from 41% (59/145) pre-admission to 18% (26/145) at 12 months (p<0.001), with little increase in the number of persons receiving disability grants. Twenty per cent (29/145) of patients required hospital readmission and this was associated with ADL functional decline (p=0.01). CONCLUSIONS There was a very high overall mortality of 42% in patients admitted to the general medical wards. Significant employment decline and readmission rates highlight the additional economic and societal burdens of hospitalisation due to medical illness in the survivors.