To determine the sensitivity and specificity of the ELISpot test, Dr. Lange and colleagues recruited 347 patients suspected of having TB, but who were either unable to produce sputum, or who had had three consecutive negative acid-fast bacilli sputum culture results. Their blood was drawn and bronchoaveolar lavage (BAL) was performed for use in ELISpot testing.
Of the 347 patients, 71 were diagnosed with active pulmonary TB. In patients with active TB, ELISpot results were positive in 65 cases (91.5 percent).
"These findings show us that positive result in the BAL ELISpot was highly indicative of and actual case of active TB," said Dr. Lange. "And a negative BAL ELISpot result almost excludes active tuberculosis."
The results confirm the findings of a 2006 pilot study, and further show that demonstration of concentration of tuberculosis-specific cells at the site of the infection is an important advance for the diagnosis of tuberculosis.
"Given the number of smear-negative cases of active TB that BAL ELISpot was subsequently able to correctly identify, about one in every two patients with smear negative pulmonary TB will benefit from BAL ELISpot testing," said Dr. Lange. "Our results indicate that ELISpot is an important advancement to rapidly distinguish acid-fast bacilli sputum smear-negative active TB from LTBI in routine clinical practice."
"Future research about the immunodiagnosis of tuberculosis will need to identify indicators of treatment success that will allow safe discontinuation of antituberculosis therapy without an increased risk of the reactivation. This will be of great clinical importance to guide the treatment of individuals with LTBI and active tuberculosis, especially in cases of drug-resistant strains of M. tuberculosis," said Dr. Lange
|Contact: Keely Savoie|
American Thoracic Society