To the Editor The study by Dr Futier and colleagues1 assessed the effect of hydroxyethyl starch (HES) vs saline on outcomes after major abdominal surgery.
Although most statistical methods appear correct, there may be an error in Table 3, which presented the effect of HES on acute kidney injury (AKI) measured by the Kidney Disease: Improving Global Outcomes (KDIGO) classification (stage 0, 1, 2, or 3). For this ordinal outcome, the authors appear to have compared groups at each level with all other levels. For example, they compared groups on whether patients had stage 1 vs all other stages (0, 2, or 3) and found a statistically significant difference (15% in the HES group vs 10% in the saline group; P = .03). However, comparing groups at each level of an ordinal variables does not make sense. One group could have a higher proportion of patients with stage 1 but a lower proportion with stages 2 and 3 and still be found “worse.” Similarly, the authors compared groups on whether patients had stage 2 vs all other stages (0, 1, or 3).
Mascha EJ. Hydroxyethyl Starch vs Saline for Volume Expansion After Abdominal Surgery. JAMA. 2020;324(2):199. doi:10.1001/jama.2020.6980
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