An asymmetric plot suggests a possible publication bias. Funnel plot asymmetry was assessed by the method of Egger’s linear regression test, a linear regression approach to measure funnel plot asymmetry on the natural logarithm scale of the OR. The significance of the intercept was AMN-107 molecular weight determined by the t test suggested by Egger (P < 0.05 was considered

representative of statistically significant publication bias) [23]. Stata statistical package version 10.0(Stata Corporation, College Station, TX) was used for the meta-analysis, using two-sided P-values. Results Characteristics of studies included in the meta-analysis Twenty-two articles were identified by the PubMed and Embase databases search. After reading HDAC inhibitor abstracts and full text of them, 6 articles met the inclusion criteria. All of them are nested case-control within cohort studies as shown in Table 1. Among the 6 studies, 2 studies were conducted in the United States and 4 were done in China, Japan, Finland and British. The number of cases and controls ranged from 93 to 230 and 186 to 9,351, respectively. The total numbers Selleck JQ-EZ-05 of cases and controls in these studies were 1,043 and 11,472. Table 1 Characteristics of case-control studies for lung cancer and IGF-I

and IGFBP-3 Study Year, location Sample size (case/control) Measurement OR(95%CI) for IGF-I OR(95%CI) for IGFBP-3 Adjusted factors in the model in original report       IGF-1 IGFBP3       Lukanova et al.[14] 2001, USA 93/186 RIA RIA 0.54(0.14–2.07) 0.90(0.28–2.85) Acyl CoA dehydrogenase Age, date of recruitment in the study, menopausal status, current smoking, time since last meal, cotinine and BMI London et al.[15] 2002, China 230/740 RIA IRMA 0.86(0.47–1.57) 0.50(0.25–1.02) Smoking Spitz et al.[16] 2002, USA 159/297 ELISA ELISA 0.64(0.31–1.33) 2.35(1.13–4.92) Age, sex, race, year of enrollment, and year of blood draw, BMI, smoking status, pack-years of smoking, exposure population Waikai

et al.[17] 2002, Japan 194/9351 IRMA IRMA 1.74(1.08–2.81) 0.67(0.45–1.01) Age, area, gender, smoking habits, and BMI Ahn et al.[18] 2006, Finland 200/400 ELISA ELISA 0.76(0.39–1.49) 0.71(0.35–1.47) Age, intervention arm, BMI, and years of smoking Morris et al. [19] 2006, British 167/498 ELISA ELISA 1.21(0.62–2.35) 1.70(0.87–3.30) Age, smoking All are nested case-control studies within cohort study. BMI indicates body mass index. IRMA, immunoradiometric assay; ELISA, enzyme-linked immunoabsorbent assay; RIA, radioimmunoassay assay. Statistical heterogeneity After performing the tests for heterogeneity for IGF-I and IGFBP-3 separately, we decided to use a fixed-effect model to obtain a summary statistic as the tests were not statistically significant (Q-value of 5.86 with df = 5, P = 0.320 for IGF-I and Q-value of 6.66 with df = 5, P = 0.247 for IGFBP-3).

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