Before taking headlines at face value, make sure the study authors have the facts right. A new meta-analysis concludes that blood transfusions after a myocardial infarction (heart attack) doubles the mortality risk and increases the chance of subsequent MI in survivors but the study is riddled with serious epidemiological fallacies that render this conclusion suspect, at best.
The meta-analysis included 10 studies published between 1966 and 2012 mostly observational with one randomized controlled trial, which evaluated over 200,000 patients. According to study authors, the data revealed that 18.2 percent of transfused patients died, compared with 10.2 percent of patients who did not receive blood, amounting to a mortality risk ratio of 2.91 associated with transfusions.
However, authors disregard the fact that anemia of sufficient severity as to require a transfusion in acute MI is in and of itself associated with worse prognosis. They also state that transfused patients tend to be older and have more advanced disease and comorbidities, which might confound analyses of morbidity and mortality, but still adhere to their conclusion that transfusions do indeed double mortality risk. Of course, being a meta-analysis, in addition to the observational nature of the study and the complete lack of any biological plausibility for such a causal link, the authors conclusions cannot be taken seriously.
Drs. Jeffrey L. Carson, of the University of Medicine and Dentistry of New Jersey in New Brunswick and Paul C. Hébert of Ottowa Hospital Research Institute urge that these findings should not discount the value of transfusions. As physicians, we believe that profound anemia is life threatening, and as a consequence, transfusions in many patients are life saving ¦Because of its many limitations, as physicians, we should not use the results of this review to justify or limit the use of red blood cells. They believe that the bottom line is that high-quality research needs to be done regarding how blood transfusions should be used. We here at ACSH echo these sentiments completely, and further note that journalists who jump to the conclusions posited by the authors should do a bit of independent contemplation before taking the leap.
