Elevated peripheral blood monocyte count is associated with prolonged postoperative hospitalization and functional decline in patients with interstitial lung diseases undergoing surgical lung biopsy.

Objective: Monocyte count and red cell distribution width (RDW) have shown prognostic potential in patients with fibrotic lung diseases. Their kinetics and prognostic usefulness of peripheral blood indices in patients with interstitial lung diseases (ILDs) undergoing surgical lung biopsy for diagnostic reasons have not been studied.

Patients and methods: We retrospectively included consecutive patients with ILD who underwent surgical lung biopsy for diagnostic purposes Between 07/11/2019 and 11/10/2022.

Results: Fifty-five (n=55) patients were included in the study. Median age was 65.0 years (95% CI: 63.0 to 66.0). Postoperative peripheral blood monocyte count on Day 1 was significantly higher compared to preoperative, perioperative, and postoperative values on Day 90 (repeated measures ANOVA, p<0.0001). Patients in the high postoperative monocyte count group had significantly increased length of postoperative hospital stay [Mann-Whitney test, p=0.007] and significantly lower Forced Vital Capacity (FVC)% predicted 3 months after surgery [Mann-Whitney test, p=0.029] compared to patients in the low postoperative monocyte count group. Postoperative RDW on Day 90 was significantly higher compared to preoperative, perioperative and postoperative-Day 1 RDW (repeated measures ANOVA, p=0.008, p=0.006, p<0.0001, respectively). Patients in the high postoperative RDW group did not have increased hospital stay (Mann-Whitney test, p=0.49) or decreased FVC% predicted at 3 months compared to patients in the low postoperative RDW group (Mann-Whitney test, p=0.91).

Conclusions: Peripheral blood monocyte count could be a prognostic biomarker for patients with ILDs undergoing diagnostic surgical lung biopsies. RDW does not seem to represent an acute phase biomarker but seems to increase over time following disease progression. Larger studies are urgently required.