Epidemiological characteristics and methodological quality of meta-analyses on diabetes mellitus treatment: a systematic review.

OBJECTIVE: Well-conducted meta-analyses (MAs) are considered as one of the best sources of clinical evidence for treatment decision. MA with methodological flaws may introduce bias and mislead evidence users. The aim of this study is to investigate the characteristics and methodological quality of MAs on diabetes mellitus (DM) treatments. DESIGN: Systematic review. METHODS: Cochrane Database of Systematic Review and Database of Abstract of Reviews of Effects were searched for relevant MAs. Assessing methodological quality of systematic reviews (AMSTAR) tool was used to evaluate the methodological quality of included MAs. Logistic regression analysis was used to identify association between characteristics of MA and AMSTAR results. RESULTS: A total of 252 MAs including 4999 primary studies and 13,577,025 patients were included. Over half of the MAs (65.1%) only included type 2 DM patients and 160 MAs (63.5%) focused on pharmacological treatments. About 89.7% MAs performed comprehensive literature search and 89.3% provided characteristics of included studies. Included MAs generally had poor performance on the remaining AMSTAR items, especially in assessing publication bias (39.3%), providing lists of studies (19.0%) and declaring source of support comprehensively (7.5%). Only 62.7% MAs mentioned about harm of interventions. MAs with corresponding author from Asia performed less well in providing MA protocol than those from Europe. CONCLUSIONS: Methodological quality of MA on DM treatments was unsatisfactory. There is considerable room for improvement, especially in assessing publication bias, providing lists of studies and declaring source of support comprehensively. Also, there is an urgent need for MA authors to report treatment harm comprehensively.

[Stoichiometric characteristics of plant and soil C, N and P in different forest types in depressions between karst hills, southwest China].

The stoichiometric properties of plant carbon (C), nitrogen (N) and phosphorus (P) and their relationships with soil were studied in six dominant plant communities in three forest types, i.e., plantation forest, secondary forest and primary forest in depressions between karst hills, southwest China. The C, N and P contents of both plant and soil had significant differences among the different forest types. Soil C and N contents were the highest in the secondary forest and the lowest in the plantation forest. Soil P content was the highest in the plantation forest and the lowest in the primary forest. Plant C and P contents were in the order of plantation forest > primary forest > secondary forest, and plant N content was the highest in the plantation forest and the lowest in the primary forest. Soil N:P,C:P and plant C:P ratios were significantly higher in the primary forest than in the other two forest types. There were no significant difference for the soil C:N ratio among the three forest types. Plant N:P ratio was the highest in the secondary forest and the lowest in the plantation forest. Plant C:N ratio was in the order of primary forest > plantation forest > secondary forest. There were significantly positive linear correlations between N and P contents, C:N and C:P ratios, C:P and N:P ratios of arbor leaves in the different forest types, and significant negative linear correlations between plant C:N and N:P ratios, and between soil C:N and N:P ratios. There were no significant correlations between plant and soil C, N, P contents and C:P ratio, suggesting that the supply of C, N and P from soil had little influence on plant C, N and P contents.