title: Significance of IFN-ɤ/IL-2 Ratio as a Circulating Diagnostic Biomarker in Extrapulmonary Tuberculosis.
abstract: Extrapulmonary tuberculosis (EPTB) remains a challenging diagnosis both for clinicians and microbiologists. We hypothesized that the profile of IFN-ɤ/IL-2 ratio in clinically diagnosed cases of EPTB would be distinct from that of age- and sex-matched healthy controls. Therefore, in our study, we have assessed the ratio of serum levels of IFN-ɤ and IL-2 in clinically diagnosed cases of EPTB to assess their potential role as diagnostic biomarkers. Sixty-nine (69) clinically confirmed EPTB cases and 69 age- and sex-matched healthy controls were included in the study. All the extrapulmonary specimens were subjected to Ziehl-Neelsen staining for acid-fast bacilli and culture on Lowenstein-Jensen (LJ) medium. Detection of serum levels of IFN-ɤ and IL-2 was carried out using commercially available ELISA kits following manufacturers' instructions. The ratio of serum levels of IFN-ɤ and IFN-ɤ/IL-2 was discriminative for the diagnosis of EPTB cases (p < 0.001), although the same was not observed with IL-2 (p > 0.05). Distribution of all biomarkers significantly differed between culture-positive and culture-negative cases (p < 0.05). Among the smear-positive and smear-negative ones, only IFN-ɤ and IFN-ɤ/IL-2 ratio could significantly differentiate (p < 0.05). Ratio of IFN-ɤ and IL-2 rather than the individual levels was the best discriminatory biomarker with the highest area under the ROC curve. Although IFN-ɤ and IFN-ɤ/ IL-2 ratio could aid in the diagnosis of EPTB, IL-2 has a limited utility in the diagnosis of EPTB. Further elaborate studies to validate these results are required.
authors.affiliation: Department of Microbiology, University College of Medical Sciences & Guru Teg Bahadur Hospital, New Delhi, India.
authors.forename: N
authors.initials: N
authors.lastname: Goyal
authors.affiliation: Department of Microbiology, Maulana Azad Medical College and Associated Hospitals, New Delhi, India.
authors.forename: B
authors.initials: B
authors.lastname: Kashyap
authors.affiliation: Department of Microbiology, University College of Medical Sciences & Guru Teg Bahadur Hospital, New Delhi, India.
authors.forename: I R
authors.initials: IR
authors.lastname: Kaur
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood*; D003430:Cross-Sectional Studies; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007371:Interferon-gamma / Q000097:blood*; D007376:Interleukin-2 / Q000097:blood*; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D014388:Tuberculosis, Lymph Node / Q000175:diagnosis*; D014396:Tuberculosis, Pleural / Q000175:diagnosis*; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis*; D014401:Tuberculosis, Urogenital / Q000175:diagnosis*; D055815:Young Adult
chemical_list: D015415:Biomarkers; D007376:Interleukin-2; D007371:Interferon-gamma