Optimum Timing of Blood Tests for Monitoring Patients with Clostridium difficile-Associated Diarrhea

Abstract

Objective

This study aimed to identify optimum timing of blood tests and suitable cutoff values when managing patients with Clostridium difficile-associated diarrhea (CDAD), in relation to early mortality.

Methods

Review of 204 patients treated as inpatients for a first episode of CDAD from January to December 2008. Differences in values during the first 7 days of CDAD for white cell count (WCC), albumin, C-reactive protein, and creatinine between those who died and survivors to 30 days were compared using Mann-Whitney U tests. Cutoff values were assessed using receiver operating characteristic curves.

Results

Overall 30-day mortality was 27% (n = 56/204). White cell counts were significantly higher in those who died on the first 3 days (P < 0.001, P = 0.015, and P = 0.001, respectively). Median WCC in those who died was 20 × 10⁹/L or greater on both days 1 and 2. Albumin was significantly different on day 1 only (P = 0.003); C-reactive protein, and creatinine did not differ significantly on any day. The highest WCC in the first 3 days produced an area under the curve of 0.718 (P < 0.001). A WCC cutoff at 20 × 10⁹/L or greater when compared with 15 × 10⁹ or greater had a higher positive predictive value (0.46 vs 0.34) and specificity (0.82 vs 0.60) but a lower sensitivity (0.49 vs 0.65). Mortality rates in the 2 groups were 46% and 34%, respectively.

Conclusions

White cell count in the first 3 days is the strongest serum predictor of mortality and should be routinely monitored. A WCC of 20 × 10⁹/L or greater may be the best cutoff value to objectively identify cases at higher risk of death.