The Value And Clinic Implication Of Combined Assay Of Interleukin-18 And Interferon Gamma On The Differential Diagnosis Between Tuberculous Or Malignant Pleural Effusion

Backgroud and ObjectiveTuberculous and malignant pleural effusion are very common in the exudation clinically. Since the treatment and prognation are obviously different, their differential diagnosis seems to be very important. Both tuberculous and malignat effusion are exudation with dominant lymocytes in cytological tests while the tumor cell found at low rate and the sensitivity of tuberculosis bacilli in direct microscope test and Zihlh- Neelsen dry is far low (0 - 1%) in that it needs the tuberculosis bacilli in effusion exceeds 10, 000/mL Even the culture for tuberculous bacilli need a 2-week or 4-week to have positive result, though the sensitivity is higher (11- 50%). open thoract pleural biopsy is a gold standard to confirm the cause of effusion because it can observe the focus directly and select to biopsy. Its sensitivity and specificity are higher than that of other methods. But this operation got more hurt and the risk is high. Therefore, to find an indirect accessory test with high sensitivity and specificity to differential diagnose Tuberculous and malignant pleural effusion will be important in clinic. Interleukin-18 (IL-18) and interferon(IFN-γ) are multiple potent cytokines, playing an important roles in regulating the immune reaction between Th1 and Th2. recent studies discovered that IL-18 and IFN-γhave a close relation with Tuberculous and malignant pleural effusion. This study is to assay the concentration of IL-18 and IFN-γin healthy people's serum, serum and effusion of tuberculous pleural and malignant effusion, to analyse the value and clinic implication of combined assay of interleukin-18 and interferon gamma on the differential diagnosis between tuberculous or malignant pleural effusion.Materials and methodsThe serum and effusion of the 34 cases of diagnosed tuberculous pleurisy and 38 cases of diagnosed malignant pleural effusion were collected from respiratory department, The First Affiliated Hospital, College of Medicine, Zhejiang University, department of tuberculosis, Hangzhou Red Cross hospital, department of respiratory disease of Shenzhou people's hospital. The serum of normal contrast group were sampled from volunteers and blood donators. Informed consent was obtained from all subjects. The pleural centesis were performed before treatment within 24 hours after admission, under the patients' consent. 10ml effusion and 5ml blood were collected, the clear part were collected after centrifuged 15min at the speed of 2000r/min, kept at -20℃until testing IL-18 and IFN-γ.Human IL-18 was assayed by the 2-antibodies sandwich biotin enzyme complex- emzyme linked immune sorption assay(ABC-ELISA). The antibody to IL-18 was coated in microplate. The IL-18 in standards and samples combined with the antibody. Adding biotinated anti- IL18 antibody, the immune complex of antibody to IL18-IL18- antibody to IL18 was formed, then horseradish peroxidase tagged streptavidin combined with biotin. After adding the emzyme OPD, the yellow color appeared. Add stop liquid , then read the optical density at 492nm wavelength. The concentration of IL-18 is direct ratio to OD value. So it can be speculated by graph a standard curve. IFN-γwas assayed by the 2-antibodies sandwich biotin enzyme complex- emzyme linked immune sorption assay (ABC-ELISA). The antibody to IL-18 was coated in microplate. The IFN-γin standards and samples combined with the antibody. Adding biotinated anti- IFN-γantibody, the immune complex of antibody to IFN-γ- IFN-γ- antibody to IFN-γwas formed. Then horseradish peroxidase tagged Streptavidin combined with biotin. After adding the emzyme OPD, the yellow color appeared. Add stop liquid , then read the optical density at 492nm wavelength. The concentration of IFN-γis direct ratio to OD value. So it can be speculated by graph a standard curve.All data are expressed as mean±SD unless otherwise indicated. The significance level was 5%. Software used for analysis was SPSS 11. 5 for Windows.ResultsThe serum IL-18 of healthy people is 152±58 ng/L, that of tuberculous pleurisy is 190±51ng/L, and that of malignancy 159±53 ng/L. Thought the serum IL-18 of tuberculous pleurisy is a little higher than that of other groups, there is no statistical signicance among these three groups (all P > 0.05). The IL-18 concentration of tuberculous effusion is 1111±190 ng/L, while that of malignant effusion 316±162ng/L. There is obvious significant between these groups (t=14.1, P<0. 01) .The serum IFN-γof healthy people is 42±26 ng/L, that of tuberculous pleurisy is 70±72ng/L, and that of malignancy 53±43 ng/L. Thought the serum IFN-γof tuberculous pleurisy is a little higher than that of other groups, there is no statistical signicance among these three groups (all P > 0.05). The IFN-γ concentration of tuberculous effusion is 1008±309 ng/L, while that of malignant effusion 31±10ng/L. There is obvious significant between these groups (t=14. 2, P<0. 01) .ConclusionsThe serum IL-18 and IFN-γbetween tuberculous and malignant effusion is no significant. But theIL-18 and IFN-γin tuberculous effusion are much higher than those of malignant effusion, there are obvious signicances between them. The sensitivity, specificity and accuracy of combined IL-18 and IFN-γtest is higher than those of single test. The combined assay of interleukin-18 and interferon-γis of great clinic implication in the differential diagnosis between tuberculous or malignant pleural effusion.