Meta-analysis in transfusion medicine

Prevalence of hepatitis E virus infection among blood donors in mainland China: a meta-analysis

BACKGROUND

The risk of hepatitis E virus (HEV) infection from blood transfusion has raised increasing concern in many countries. Several transfusion-transmitted cases have been described in the United Kingdom and Japan. The objective was to investigate the prevalence of HEV infection among Chinese blood donors and analyze the potential risk of HEV infection through blood transfusion in China.

STUDY DESIGN AND METHODS

Major English and Chinese research databases were used as background research for the study of locations, years, and the number of HEV infections among blood donors in China. The pooled, estimated rate of HEV infection was calculated. Subgroup analyses, for age, sex, and alanine aminotransferase (ALT) levels were performed using software for comprehensive meta-analysis.

RESULTS

The pooled rates of anti-HEV IgM- and anti-HEV IgG-positive donations were 1.09% (95% confidence interval [CI], 0.95%-1.26%) and 30% (95% CI, 25%-34%), respectively. The prevalence of anti-HEV IgM was significantly higher in donors with elevated ALT (4.34%) compared with the rate in donors with normal ALT (1.35%; χ²  = 39.66, p < 0.01). The anti-HEV IgM and IgG rates were higher in the Southwest region (1.58 and 41%, respectively) compared to the rates in other regions of China (chi-square test, p < 0.05). The anti-HEV IgG rate was also significantly higher in donors 30 years and older compared with donors between 18 and 29 years of age (39% vs. 22%, respectively; χ²  = 1457.10, p < 0.01). Genetic analysis of HEV from RNA-positive donors indicated that the majority of HEV infections were Genotype 1 (19/33 = 58%), while the remaining 14 isolates were Genotype 4 (14/33 = 42%; χ²  = 0.758, p > 0.05).

CONCLUSION

Qualified donations after routine blood donor screening still carry a potential risk for transmitting HEV. The major genotypes in Chinese donors in this study were Genotypes 1 and 4.

Meta-analysis of controlled clinical trials studying the efficacy of rHuEPO in reducing blood transfusions in the anemia of prematurity

BACKGROUND

Recombinant human EPO (rHuEPO) has not gained broad acceptance in the treatment of the anemia of prematurity, because its efficacy in diminishing RBC transfusions is questionable. Meta-analysis was used to investigate the extent and reasons for variation in the results of published clinical trials.

STUDY DESIGN AND METHODS

Prospective controlled trials published from 1990 through 1999 were retrieved; 21 met the criteria for meta-analysis. Calculated across these studies were the summary OR of RBC transfusion in treated neonates as compared with controls and the summary mean difference between controls and treated neonates in the volume of RBCs transfused and the number of RBC transfusions per infant. Twelve study descriptors were examined as possible reasons for the variation in results.

RESULTS

Results of 21 eligible studies varied widely (p<0.001 for the Q test statistic), and this variation persisted in most analyses when studies were stratified by individual study descriptors. When the difference in volume of RBCs transfused was the outcome measure, variation was modest across the four studies with highly desired characteristics (i.e., high blindness and design quality scores, "conservative" transfusion criteria, and the majority of neonates weighing <1 kg at birth), and treatment with rHuEPO reduced RBC transfusions by an average of 11.0 mL per kg (p<0.001).

CONCLUSION

Benefit from rHuEPO is detected across high-quality studies using conservative RBC transfusion criteria. However, there is extreme variation overall in the findings of available trials, and-until this variation is accounted for-it is premature to recommend rHuEPO as standard treatment for the anemia of prematurity.

Meta-analysis in hematology and oncology

In 1992, a review article about meta-analysis identified only 15 meta-analyses of randomized, controlled trials of cancer therapy. Since then, the total number of meta-analyses in this field has increased almost sixfold. More importantly, the number of randomized, controlled trials in this discipline has also grown tremendously. The expansion in the literature will provide a fertile ground for future meta-analyses. The quality of the recent publications has also improved. An ongoing world-wide effort, the Cochrane Collaboration, is systematically assembling and synthesizing several hundred thousand randomized, controlled trials to improve the delivery of health care. Meta-analysis has many important advantages. It allows the viewing of the complete picture of the evidence. The advent of meta-analysis has sensitized researchers to issues of quality and has improved methodology in clinical research. Detection and explanation of bias and heterogeneity are prime objectives of meta-analysis in clinical research. An array of methods has been developed that allows a better understanding of bias and heterogeneity, beyond simple averaging of results from diverse studies. Meta-analyses of individual patient data, in particular, may promote the development of international collaborations. Several examples of their application are already available in oncology. Meta-analysis may point out deficiencies in the study design of past and current studies, suggest the need for new studies, and inform researchers about the size and design of these studies. In the end, meta-analysis helps to integrate evidence and make recommendations for medical care and medical practice.

Transfusion of white-cell containing allogeneic blood components and postoperative wound infection: effect of confounding factors

Randomized controlled trials (RCTs) of the relationship between allogeneic transfusion and post-operative bacterial infection at any site have generated discordant results, but have suggested an association of transfusion with wound infection. To examine the specific association of perioperative transfusion with wound infection, we reviewed the records of 964 consecutive patients undergoing elective colorectal cancer resection at our hospital. Diagnoses of wound infection were made retrospectively by the Centers for Disease Control criteria, and transfusion was defined as number of units of white-cell containing allogeneic blood components received. The probability of wound infection in association with the transfusion was calculated following adjustment for the effects of 12 confounders that had not been previously considered in combination. These factors related to severity of illness, difficulty of operation and risk of wound infection. Wound infection developed in 39 (11.4%) transfused patients, as compared to 24 (3.9%) untransfused subjects (P < 0.0001). In the multivariate analysis, there was a trend suggesting an adverse transfusion effect, which amounted to a 7% increase in the risk of wound infection per unit of red cells or platelets transfused (relative risk [RR] = 1.07; 95% confidence interval for RR = 0.98-1.16; P = 0.1241). This marginally significant effect was related to post-operative (P = 0.1274), rather than perioperative (P = 0.3061), transfusion. We conclude that allogeneic transfusion may perhaps be associated with a small increase in the risk of post-operative wound infection, but this small effect can be established only by RCTs enrolling several thousand patients. The modest magnitude of the effect may have been responsible for the disagreements among the published RCTs.