A Field Trial Evaluating the Quantiferon Gold Tuberculosis Test in an Endemic Population

Quantiferon Gold (QG) is a highly sensitive and specific assay for Mycobacterium tuberculosis (MTB) in controlled conditions. We wanted to determine its usefulness when specimens were obtained locally but analyzed after storage and shipping at a distant facility. Methods: Healthcare workers at a Caribbean island community hospital where MTB and other mycobacteria are endemic and BCG receipt is common comprised the study population. All patients received BCG. They had a minimally13 mm induration positive tuberculin skin test and negative chest x-ray within the last one year. Venous blood specimens were collected and incubated at 37degrees centigrade. After overnight incubation (minimally 16 hours, < 24 hours) the specimens were spun at 2000-3000 rpm for 10 minutes and refrigerated at 40°F. After 12 days of collecting, specimens were shipped by express mail to our genetics laboratory for testing, a distance of over 4,000 miles. Upon receipt the specimens were again refrigerated and batch tested four days later. Results: There were 25 specimens in which we had complete data. Nine (36%) of the specimens were positive. Discussion: The QG test can be employed in less than ideal conditions. Venous blood specimens can be obtained and processed in field conditions. They can then be shipped by express mail, and batch analyzed. QG can also be used where BCG receipt and other mycobacterium infections are common