Simple Cough Test Spots Tuberculosis

Worked as well as invasive procedure, South African study says

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HealthDay Reporter

THURSDAY, Jan. 6, 2005 (HealthDayNews) -- Diagnosing tuberculosis in children may be a simpler task than doctors have thought, a new South African study suggests.

A quick, easy test where kids simply cough up one specimen of sputum is as effective at diagnosing tuberculosis (TB) as the expensive, complicated and widely used procedure called gastric lavage, the researchers report.

"Our trial establishes that a single induced sputum is very useful for diagnosing TB in children, even in infants," said Dr. Heather J. Zar, director of the department of pediatric pulmonology at the University of Cape Town. She is the author of a report on the procedures that appears in the Jan. 8 issue of The Lancet.

"The current standard of diagnosis is three sequential gastric lavages, which usually require a child to be hospitalized for two days with an overnight starve, which is unpleasant for child and health-care provider," Zar added.

The sputum test has been discredited because "traditional teaching has been that it is not possible to get sputum from infants and young children," Zar said. "However, this study shows that this is incorrect, and raises more possibilities for the use of sputum for diagnosing other respiratory illnesses in young children."

Quick diagnosis of tuberculosis is obviously important in South Africa and other countries where AIDS is widespread, said Dr. Lee B. Reichman, director of the New Jersey Medical School National Tuberculosis Center.

"Tuberculosis and HIV are inextricably linked," Reichman explained. "Tuberculosis is by far the greatest killer of persons infected with HIV. But tuberculosis is preventable and treatable when diagnosed."

A simpler diagnostic test would also be helpful in the United States, Reichman added. "Because of the fact that everyone thinks that tuberculosis has gone away, there haven't been any new diagnostic tests in years. But tuberculosis certainly hasn't gone away," he said.

TB incidence has been declining steadily by 5 percent to 6 percent a year in the United States, "but the curve is sort of leveling off," he said. The decrease in 2003, the last year for which data are available, was less than 2 percent, and the incidence of TB increased in 18 states, including New York, California and Texas.

There were 14,874 cases of tuberculosis in the United States in 2003, 55 of them among children under the age of 5 and 367 in children aged 5 to 14, the U.S. Centers for Disease Control and Prevention has reported.

The South African physicians studied 250 children aged 1 month to 5 years who were admitted for suspected tuberculosis. Sputum induction and gastric lavage were done on three consecutive days. Tests found that 62 of the children were infected. Sputum induction detected TB in 54 of the children, while gastric lavage was positive in only 40 of them.

A research letter in the same issue of the journal described successful use of a method called the string test for TB, in which sputum is induced by having someone swallow a string. The method was used for 228 HIV-infected patients, reported physicians at the Hospital Nacional Dos de Mayo in Lima, Peru. The use of the string test followed by sputum induction detected tuberculosis in 14 patients, compared to eight who had only sputum induction.

"The string test is safe and effective for retrieval of useful clinical specimens," the researchers said. Reichman described it as a completely new method that requires further study.

More information

The basics of tuberculosis are described by the American Lung Association.

SOURCES: Heather J. Zar, M.D., director, department of pediatric pulmonology, University of Capetown, South Africa; Lee B. Reichman, M.D., director, New Jersey Medical School National Tuberculosis Center, Newark; Jan. 8, 2005, The Lancet

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