To the Editor:
A recent retrospective study in the American Journal of Medicine shed light on the question of how often to monitor blood counts during acute gastrointestinal bleeding. The authors conclude that more frequent testing is associated with similar outcomes, but more red cells transfused, and suggest that this means that monitoring is too frequent.
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I have concerns about the authors’ interpretation of the data.First, the authors state that their propensity score matching adjusted for “severity of bleeding.” However, the parameters included in this analysis were patient characteristics on presentation, such as initial hemoglobin and vital signs. One potential explanation for the increased amount of blood transfused in the more-frequently monitored group is that monitoring was performed more often because the team noted a more rapid decrease in hemoglobin, higher transfusion requirements to maintain hematocrit, persistent hypotension, or other signs of more bleeding. If that were the case, more frequent monitoring would be the effect of greater transfusion requirements, rather than the cause, as the authors suggest. Nor did they assess the extent of bleeding or the appropriateness of the transfusions, instead apparently assuming that more transfusion was inappropriate.
Second, the authors point to the lack of a statistically significant mortality difference among the matched groups but note higher mortality in the less-frequently monitored group in the entire cohort. They do not mention if this is statistically significant (doubtful), nor do they mention a trend of similar magnitude toward higher mortality in the less-monitored group within the matched cohort as well. They state that the difference within the entire (not matched) cohort is not due to differences in disease severity because of propensity matching. However, this group was not matched, so this conclusion is not consistent with the data. Finally, they conclude that higher mortality could be the result of increased monitoring. However, the data show a trend toward higher mortality in the less-monitored group (in both the unmatched and matched cohorts), so their conclusion is the opposite of what the data show.
In sum, their analysis of the data is inadequate to conclude that more frequent testing within their cohort was associated with excessive transfusion or worse outcomes, due to inadequate matching, failure to assess appropriateness of transfusion, and misinterpretation of the mortality data. Their recommendation to change practice in order to reduce the alleged harms of testing is not supported by the evidence presented.
Reference
- Hemoglobin monitoring in acute gastrointestinal bleeding: Are we monitoring blood counts too frequently?.Am J Med. 2021; 134: 682-687
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Conflict of Interest: None.
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© 2021 Elsevier Inc. All rights reserved.
