Alere Determine™ TB LAM Ag
Features
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Screen for HIV-associated TB in patients with advanced immunosuppression.
Point-of-care test
with results in just 25 minutes.
Convenient urine sample.
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Rapid Rule-in
TB-HIV Co-infectionThe Alere Determine™ TB LAM Ag test empowers you, at the point-of-care, to screen for HIV-associated TB, providing results in minutes.
TB is the leading cause of morbidity and mortality in patients with HIV, particularly in those with the lowest CD4 cell counts.
These patients are difficult to diagnose, with tools such sputum smear microscopy and chest radiography offering low sensitivity and specificity in this patient group.
Paradoxically it is these patients that have the greatest need for rapid and accurate diagnosis, permitting fast initiation of TB treatment.
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Any photos displayed are for illustrative purposes only.
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TB LAM
Antigen DetectionLipoarabinomannan (LAM) is a structurally important component of the outer cell wall of mycobacteria. It is a 17.5 kDa glycolipid found at the surface of the cell, where it acts as an immunomodulator, readily interacting with the host receptors1.
During a TB infection, LAM antigen is shed from metabolically active or degrading cells, is cleared by the kidney and detectable in urine.
Because it is a product of the bacteria, it has the potential to identify only active TB infections, making it an attractive diagnostic target2.
This stands in contrast to lateral flow TB antibody (Ab) tests, which are highly variable in their performance and are imprecise, producing high proportions of false positive and false negative results. The World Health Organisation has recommended against the user of TB serology tests3.
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HIV-associated TB
The Alere Determine™ TB LAM Ag test is targeted for the most vulnerable and hard to diagnose patients.
HIV infected patients with advanced immunosuppression and low CD4 count are at high risk of TB infection. TB disease in these patients often remains unidentified, preventing the commencement of effective treatment, which if initiated early, can reduce hospital stay and mortality.
Traditional TB diagnostics such as sputum smear microscopy perform poorly in these patients, with sensitivity decreasing as the CD4 cell count drops. In contrast, the TB LAM Ag test shows an increase in sensitivity as the CD4 cell count drops and offers the greatest sensitivity in patients with CD4 cell count less than 200 cells/µL4.
As demonstrated in a recent study of ambulatory HIV infected patients referred for ART, the TB LAM Ag test was able to correctly identify the majority of tuberculosis cases in patients with CD4 cell count less than 50 and less than 100 cells per µL4.
* Adapted from Lawn SD et al., “Diagnostic accuracy of a low-cost, urine antigen, point-of-care screening assay for HIV-associated pulmonary tuberculosis before antiretroviral therapy: a descriptive study.” Lancet Infect Dis. 2012 Mar;12(3):201-9. -
What is LAM?
With Dr Stephen Lawn
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Detect pulmonary and extrapulmonary TB
Detection of the TB LAM antigen allows you to diagnose both pulmonary and extra pulmonary TB.
Many TB diagnostic tools rely on patient samples acquired from the site of disease, such as sputum, cerebrospinal fluid and lymph node aspirates. Not all patients are able to produce sputum or may have an infection from a site that hasn’t been sampled.
The ability to detect both pulmonary and extrapulmonary TB from one sample type is particularly useful in HIV infected patients who have a higher prevalence of extra pulmonary TB and often find it difficult to produce sputum.
Convenient Urine Sample
The Alere Determine™ TB LAM Ag test uses unprocessed urine as the validated sample type.
Urine is an ideal sample as it is not specific to the location of an infection, it is readily available, it doesn’t produce hazardous aerosols and poses a lower biohazard and infection risk to health care workers, laboratory staff and other patients.
Once the urine sample is added to the test, results will be ready in just 25 minutes. Sample collection is quick and easy, and with no sample preparation required, results will be available in no time.
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TB LAM Ag in Combination
Increases SensitivityWhile the Alere Determine™ TB LAM Ag test offers clinical utility in its own right, enhanced power comes through combination with methods such sputum smear microscopy or the Xpert® MTB/RIF test.
This additive effect was demonstrated by Lawn4 showing an increase in sensitivity when results from the TB LAM Ag test were combined with sputum smear microscopy. Using this method, they were effectively able to rule-in 72.2% of TB suspects with a CD4 cell count less than 50.
A similar result was demonstrated by Peter5 whereby they were able to rule-in 71% of M.tb culture positive patients with this diagnostic combination.
The Xpert® MTB/RIF test faces sensitivity challenges in diagnosing TB in HIV infected patients. It demonstrated 58% sensitivity in HIV infected patients with advanced immunosuppression, using one sputum sample. The addition of a second sample increase sensitivity to 78%, however this may not be feasible for many clinics4.
The addition of a simple, inexpensive urine TB LAM Ag test has demonstrated an increase in sensitivity, up to 83.3% in patients with CD4 cell count less than 50, and could help to identify more TB positive patients.
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Detect sputum smear
negative patientsThe presentation of pulmonary TB changes with an HIV infection.
HIV infected patients often have a lower sputum bacillary load, resulting in a higher proportion of sputum smear negative patients. TB diagnosis in these patients can be delayed or missed; these patients have an exceptionally high mortality rate.
In a study of hospitalised HIV infected patients with advanced immunosuppression, the TB LAM Ag rapid test was able to detect more than half of the smear negative/sputum scarce patients5.
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References
- Wood R, Racow K, Bekker LG, Middlekoop K, Vogt M, Kreiswirth BN, Lawn SD. Lipoarabinomannan in urine during tuberculosis treatment: association with host and pathogen factors and mycobacteriuria. BMC Infect Dis. 2012 Feb 27;12:47.
- Shah M, Variava E, Holmes CB, Coppin A, Golub JE, McCallum J, Wong M, Luke B, Martin DJ, Chaisson RE, Dorman SE, Martinson NA. Diagnostic Accuracy of a Urine Lipoarabinomannan Test for Tuberculosis in Hospitalized Patients in a High HIV Prevalence Setting. J Acquir Immune Defic Syn. 2009 Oct 1;52(2):145-51.
- WHO Commercial Serodiagnostic Tests for Diagnosis of Tuberculosis, Policy Statement 2011 [Internet]. Geneva: World Health Organisation; 2011 [cited 2012]. Available from: http://whqlibdoc.who.int/publications/2011/9789241502054_eng.pdf
- Lawn SD, Kerkhoff AD, Vogt M, Wood R. Diagnostic accuracy of a low-cost, urine antigen, point-of-care screening assay for HIV-associated pulmonary tuberculosis before antiretroviral therapy: a descriptive study. Lancet Infect Dis. 2012 Mar;12(3):201-9.
- Peter JG, Theron G, van Zyl-Smit R, Haripersad A, Mottay L, Kraus S, Binder A, Meldau R, Hardy A, Dheda K. Diagnostic accuracy of a urine LAM strip-test for TB detection in HIV-infected hospitalised patients. Eur Respir J. 2012 Feb 23 (Epub ahead of print).
* Adapted from Lawn SD et al., “Diagnostic accuracy of a low-cost, urine antigen, point-of-care screening assay for HIV-associated pulmonary tuberculosis before antiretroviral therapy: a descriptive study.” Lancet Infect Dis. 2012 Mar;12(3):201-9.
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