A Benhaddad | PubMed Health

PubMed1998

Fibrinogen is negatively correlated with aerobic working capacity in football players.

While it is well established that blood viscosity is decreased in sportsmen and related to fitness, the involvement of fibrinogen in this relationship is less well defined. Relationships among fitness, rheology and fibrinogen were investigated in 32 football players (age 17-33 years: 19 professionals and 13 leisure players). A submaximal 25 min exercise-test was performed and allowed the calculation of aerobic working capacity. Aerobic working capacity (W170 and VO2 max) was negatively correlated to fibrinogen (r = -0.531, p < 0.01 and r = -0.623, p < 0.01), while on the whole sample the correlation to viscosity and erythrocyte aggregation was not significant. When subjects were divided into two subgroups according to their plasma fibrinogen concentration, the aerobic working capacity (either expressed as W170 or VO2 max) is higher when plasma fibrinogen level is lower than 2.7 g/l. Thus, there is a highly significant negative correlation between fibrinogen and fitness in these sportsmen, independent of blood rheology. These data suggest that rheology and fibrinogen are to some extent separate determinants of an individual's fitness.

Adolescent↗

PubMed1997

Discrepancies between meta-analyses and subsequent large randomized, controlled trials.

BACKGROUND: Meta-analyses are now widely used to provide evidence to support clinical strategies. However, large randomized, controlled trials are considered the gold standard in evaluating the efficacy of clinical interventions. METHODS: We compared the results of large randomized, controlled trials (involving 1000 patients or more) that were published in four journals (the New England Journal of Medicine, the Lancet, the Annals of Internal Medicine, and the Journal of the American Medical Association) with the results of meta-analyses published earlier on the same topics. Regarding the principal and secondary outcomes, we judged whether the findings of the randomized trials agreed with those of the corresponding meta-analyses, and we determined whether the study results were positive (indicating that treatment improved the outcome) or negative (indicating that the outcome with treatment was the same or worse than without it) at the conventional level of statistical significance (P<0.05). RESULTS: We identified 12 large randomized, controlled trials and 19 meta-analyses addressing the same questions. For a total of 40 primary and secondary outcomes, agreement between the meta-analyses and the large clinical trials was only fair (kappa= 0.35; 95 percent confidence interval, 0.06 to 0.64). The positive predictive value of the meta-analyses was 68 percent, and the negative predictive value 67 percent. However, the difference in point estimates between the randomized trials and the meta-analyses was statistically significant for only 5 of the 40 comparisons (12 percent). Furthermore, in each case of disagreement a statistically significant effect of treatment was found by one method, whereas no statistically significant effect was found by the other. CONCLUSIONS: The outcomes of the 12 large randomized, controlled trials that we studied were not predicted accurately 35 percent of the time by the meta-analyses published previously on the same topics.

Humans↗