Evaluation of QuantiFERON-TB Gold in Diagnosis of Tuberculous Pericardial Effusion

Abstract

Background: Prompt treatment of tuberculous pericarditis can save lives, but definite diagnosis requires detection and isolation of the tubercle bacilli from pericardial fluid and/or biopsy which is often delayed and difficult. Objectives: To evaluate the diagnostic role of QuantiFERON-TB Gold test (QFT-G) as a rapid non invasive immunological assay in diagnosis of tuberculous pericarditis with pericardial effusion in comparison to Adenosine deaminase enzyme (ADA) activity and Polymerase chain reaction (PCR) either individually or in combination. Subjects and methods: 27 patients suffering of pericarditis accompanied with pericardial effusions highly suspicious to be tuberculous (clinically and radiographically) were subjected to pericardial fluid aspiration and biopsy, Ziehl-Neelsen stain, culture and histopathological examination(biopsy) for tuberculosis were done for each sample. Pericardial fluid was submitted to Polymerase chain reaction and measurement of adenosine deaminase activity and finally QuantiFERON-TB Gold test in blood was done. Results: Out of 27 probable tuberculous pericarditis patients with pericardial effusion, 19 were definite positive cases. Considering the value of 40 U/L ADA activity , 16/19 cases were positive so the sensitivity was 84.2% which was the same as the results of QuantiFERON-TB Gold test while there were 10 PCR positive cases, so PCR sensitivity was 52.6%. There were 2 positive ADA and one QuantiFERON-TB Gold positive results among the 8 culture negative cases, while none was detected by PCR , so its specificity was100% while (QFT-G) specificity was 87.5% and ADA 75%. The sensitivity, specificity, PPV and NPV of combined QFT-G test and PCR results were 89.5%, 87.5%, 94.4% and 77.8% respectively. While the sensitivity, specificity, PPV and NPV combined QFT-G with ADA results were 84.2%, 75%, 88.9% and 66.7% respectively. Conclusion: QuantiFERON-TB Gold test have good sensitivity and specificity for diagnosis of tuberculous pericardial effusion. The best combined sensitivity and specificity in the current study were reported between PCR and QuantiFERON test results but it is not much greater than that of QuantiFERON test alone. So, QuantiFERON-TB Gold test can be used as an adjunct rapid immunological non invasive test for diagnosis of tuberculous pericardial effusion. However negative QuantiFERON-TB Gold assay does not exclude the disease because of the low NPV of this assay.