| Abstract: Problem statement: After HIV infection, TB is the most common cause of mortality due
to a single infectious agent. Until 1985, tuberculosis cases in the world were decreasing every year, but
then with the prevalence of HIV infection, TB cases are increasing every year. Obviously, with this
prevalence of tuberculosis, the best way to control it is to track the patient and identify the people with
latent TB and treat them. One third of the world population is infected with latent tuberculosis micro
bacterium and tuberculosis causes two million deaths a year. Identification of people with latent TB
infection is the primary aim to eradicate TB in the community. The method to measure gamma
interferon in the blood called QuantiFERON®-TB Test is a promising diagnostic test for diagnosing
latent TB infection and is more beneficent than compared to PPD. The aim of this study is to
compare IFN-δ test and PPD test in diagnosis of patients with latent TB. Approach: In a crosssectional
descriptive-analytic study on 76 patients referred to the clinic or infectious diseases ward of
Imam Reza or Sina hospitals or Tabriz University of Medical Sciences during 2007 and 2008, the
patients whose CXR had fibrotic images or calcification compatible with latent TB infection were
included in the study and the correlations between IFN-δ and PPD tests was evaluated. Results: Mean
age of the patients in this study was 64.96±4.54 years with minimum 43 and maximum 81 of
age. About 33.3% of people under study had a positive PPD test and 4% of the patients had a positive
IFN-δ
and the correlation coefficient between IFN-δ test
and PPD test was estimated at 0.376
(p<01/0). Age and gender had no effect on positivity of the results of PPD test and IFN-
δ tests. Conclusion: Capability of IFN-δ test in diagnosis of latent tuberculosis infection is comparable
to that of PPD test; however, the correlation coefficient between the two tests was low and also, unlike
other studies, gender and age had no effect on positivity or negativity of PPD and IFN-δ tests. |