Letters Section Editor: Stephen J. Lurie,
MD, PhD, Senior Editor.
To the Editor: Dr Imai and colleagues1 investigated the association between changes in
plasma levels of soluble Fas ligand and changes in creatinine in patients
with acute respiratory distress syndrome (ARDS). However, I disagree with
their method of computing the magnitude and direction of correlation.
The plasma samples were obtained from patients with ARDS treated with
either conventional strategy (control group) or protective ventilatory strategy
(lung protection group) in a previous randomized clinical trial.2 The
authors reported that the mean plasma levels of soluble Fas ligand were significantly
higher in the control group compared with the lung protection group at 2 different
time points. This means that different treatment strategies changed the characteristics
of soluble Fas ligand. In addition, the authors illustrated the association
between changes in plasma levels of soluble Fas ligand and changes in levels
of creatinine. The authors' figure indicates that the control group had a
positive association, but that the lung protection group had a negative relationship.
As a consequence, the correlation coefficient estimated from combining these
2 unique groups is apparently incorrect. The authors should have assessed
and reported the relationship in the control group and the lung protection
Kuo Y. Apoptosis and Renal Function in Patients With Acute Respiratory Distress Syndrome—Reply. JAMA. 2003;290(4):461-462. doi:10.1001/jama.290.4.461-a