(RxWiki News) Blood tests are one method that has been relied on to diagnosis tuberculosis (TB). Now the World Health Organization has warned that such blood tests can frequently be inaccurate and lead to unsuitable treatments.
In a recent policy recommendation, the WHO cautioned that blood tests checking for TB could be potentially harmful to public health and urged countries to ban the unapproved blood tests.
"Ask your doctor for a microbiological or molecular tests as a TB diagnostic tool."
WHO instead asks that TB be diagnosed through more accurate microbiological or molecular tests because testing for antibodies or antigens in the blood can be difficult. Patients may receive false positive or negative tests that are ultimately determined to be inaccurate.
Dr. Mario Raviglione, director of WHO Stop TB Department, said serological blood tests equate to "bad practice," because inconsistent and imprecise results can put patients' lives in danger.
This marks the first time WHO has issued a negative policy recommendation regarding TB diagnosis. Each year about 1.7 million die from TB, a highly contagious disease that mostly affects the lungs.
The recommendation only apples to blood tests for active TB, of which at least 18 are commercially available for about $30 a test. WHO has not yet issued a recommendation in response to blood tests for dormant TB. The policy recommendation came after a yearlong analysis of 94 studies, which showed overwhelming evidence that blood tests too often produced inaccurate results.
In some cases patients were mistakenly told they had recovered from the illness, which could have resulted in death as a result of untreated TB or transmission to others. The review also acknowledged an unacceptable number of false positives for TB. Those patients then underwent unnecessary treatment and were prone to premature death since the true cause of their illness had not been diagnosed.
Dr. Karin Weyer, coordinator of TB Diagnostics and Laboratory Strengthening for the WHO Stop TB Department, said the blood tests for TB were often most popular in countries with weak regulations about procedures for diagnosing illnesses. Many allowed promotion of questionable marketing incentives that did not benefit the health of patients.