SA researchers find urine test better for rapid TB testing

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With South Africa being one of the countries with the highest burden of tuberculosis (TB) in the world, it’s imperative that we make fast, accurate diagnoses of this disease.

According to the World Health Organization (WHO) about 1% of the population develops TB each year. Combine this with HIV/Aids as the biggest killer in the country, and you have a lethal combination of HIV and TB – and the sooner doctors can make a diagnosis, the better.

A study published this week by the University of Cape Town (UCT) shows that among hospitalised patients with HIV, a simple and inexpensive urine test made more TB diagnoses in the first 24 hours of admission than rapid sputum-based tests.

Professor Graeme Meintjes, one of the researchers involved in the study, said the results build on findings of other UCT researchers that this urine test can reduce mortality among HIV-infected patients admitted to hospital by speeding up the diagnosis of TB.

“The findings of these studies challenge the dogma that the first place to look for TB is in the sputum.

“Among a select group of patients (HIV-infected patients with very weak immune systems admitted to hospital) a combination of tests is required.”

These include urine and sputum tests, and will allow doctors to start appropriate treatment immediately.

Urine test is faster

The study examined 427 patients with HIV infection admitted to the medical wards that were screened for TB using sputum, urine and blood tests. In total, one in three (33%) of these patients was diagnosed with TB.

Among patients with TB, sputum microscopy and sputum Xpert diagnosed TB within 24 hours of admission in 19% and 27%, respectively, compared to 38% using the urine Determine TB-LAM assay.

The urine test was particularly useful for diagnosing TB in the patients with the lowest CD4 counts or weakest immune systems, as well as those who were anaemic.

Sputum vs. urine tests

Traditionally sputum samples were sent to the laboratory for examination, but it is well recognised that this approach often fails in patients with HIV infection. In many of these patients, TB spreads from the lungs to the blood and other organs in the body due to poor immunity.

Additionally, there may be few or no TB bacteria found in their sputum, either because they are too weak or ill to produce a good sputum sample, or because of less TB cavity formation in their lungs.

According to the researchers the urine test was more effective because of the difficulty of obtaining a sputum specimen from many patients on admission. Whereas almost all patients, even those were very ill, could provide a urine sample. – Health24

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