The assumption of fixed-effects model is based on that the true effect of the each trial is same. However, the assumption of random-effects model is based on that the true effect of included trials is normal distributed. The total variance is equal to the sum of within-trial variance and between-trial variance under the random-effects model. There are many estimators of the between-trial variance. The aim of this paper is to give a brief introduction of the estimators of between-trial variance in trial sequential analysis for random-effects model.
Objectives To evaluate the methodological quality of published clinical practice guidelines for benign prostatic hyperplasia. Methods PubMed, EMbase, CNKI, WanFang Data, VIP and CBM databases, website of Yimaitong, and international authoritative guide platforms were electronically searched to collect the relevant clinical practice guidelines or consensus for benign prostate hyperplasia. The retrieval covered the time up to December 13th, 2016. Literatures were independently screened by 2 reviewers. After data extraction, the methodological quality of included guidelines was evaluated by 4 reviewers using the AGREE Ⅱ. Each domain score was calculated and the intraclass correlation coefficient was used to evaluate the consistency among the reviewers. Results A total of 15 clinical practice guidelines were included. The mean scores for the six domains in AGREE Ⅱ were: 72%, 38%, 30%, 58%, 16%, and 40%, respectively. The intraclass correlation coefficient was larger than 0.87, which indicated the total consistency was well. Conclusions The quality of clinical practice guidelines for benign prostatic hyperplasia is not satisfactory as expected. They are heterogeneous in quality and some requires improvement. Guidelines are required to be further developed in methodology in future, especially in three domains, including participants, preciseness and applicability of the design.