Emergency-granulopoiesis trajectory, but not the CD4/NK lymphocyte trajectory, is directionally reproduced as a correlate of sepsis mortality: a cross-cohort transcriptomic study with external testing and clinical-analogue triangulation

In early sepsis the direction in which blood immune-cell transcriptional programmes move may carry prognostic information beyond a single baseline measurement, but whether such trajectory associations survive independent testing is unknown. We scored five immune modules, frozen before analysis, in three public longitudinal whole-blood microarray sepsis cohorts and fitted a logistic model ladder fixed in advance to the change per 24 hours in the two cohorts with mortality data (82 patients, 24 deaths), pooling by inverse-variance fixed-effect meta-analysis with Benjamini-Hochberg control. No association survived correction for multiple testing. The two leading signals were a rising CD4/NK lymphocyte trajectory associated with lower mortality (pooled odds ratio 0.53, 95% confidence interval 0.31 to 0.90) and a rising emergency-granulopoiesis trajectory associated with higher mortality (1.60, 0.92 to 2.79), both per one standard deviation. We then tested both in an independent transcriptomic cohort with serial sampling (63 patients, 15 deaths), scored by the identical frozen method, and against their cell-count analogues in an intensive-care database of 12,607 adults meeting Sepsis-3 criteria, of whom 744 to 4,206 had the serial measurements each analogue required. Independent testing separated the two signals, in the order opposite to the one discovery had suggested. The emergency-granulopoiesis association was reproduced in direction and effect size without reaching conventional significance on its own (validation odds ratio 1.72, 0.92 to 3.20, p=0.088; pooled 1.65, 1.09 to 2.50), was positive in all nine sensitivity analyses, each fixed before the estimates were examined, and was supported by two of its three analogues, including the neutrophil-to-lymphocyte ratio (1.31, 1.20 to 1.42). The CD4/NK association did not reproduce (1.06, 0.59 to 1.89), was null in the window most favourable to it, and received no support from an analogue well powered to detect the discovery effect. The discovery signal that looked most consistent failed independent testing.