# Abnormal serum phosphorus was associated with the outcome of community-acquired pneumonia

## TL;DR

Abnormal blood phosphorus levels, both too low and too high, are linked to higher death rates in patients with pneumonia.

## Contribution

This study identifies severe hypophosphatemia and hyperphosphatemia as independent risk factors for in-hospital mortality in CAP patients.

## Key findings

- Severe hypophosphatemia (Grade 2) was associated with 3.7-fold higher mortality risk after adjusting for confounders.
- Hyperphosphatemia was linked to a 5.2-fold higher mortality risk after adjustment.
- In-hospital mortality rates increased with abnormal serum phosphorus levels.

## Abstract

The present study aimed to explore the relationship between serum phosphorus levels and outcomes in patients with community-acquired pneumonia (CAP).

This research was a retrospective, single-center study conducted on adult patients who were hospitalized with CAP at The First Hospital of Qinhuangdao City, Hebei Province, China, between January 2015 and December 2018. The primary outcome was in-hospital mortality. Participants were categorized into four groups: the normal serum phosphorus group (0.81–1.45 mmol/L), the hypophosphatemia group (Grade 1, 0.48–0.80 mmol/L), the hypophosphatemia group (Grade 2, <0.48 mmol/L), and the hyperphosphatemia group (>1.45 mmol/L).

This study included 1,936 CAP inpatients. The in-hospital mortality rates were 2.5, 4.4, 11.1, and 18.0% in the normal phosphorus group, the hypophosphatemia groups (Grades 1 and 2), and the hyperphosphatemia group, respectively. In the univariate logistic regression analysis, the in-hospital mortality rates for the hypophosphatemia (Grade 2) and hyperphosphatemia groups were 4.892 (95% CI: 1.410–16.969, p = 0.012) and 8.572 times (95% CI: 4.912–14.960, p < 0.001) higher, respectively, compared to the normal phosphorus group. After adjusting for confounding factors, hypophosphatemia (Grade 2) (OR = 3.715, 95% CI: 1.013–13.633, p = 0.048) and hyperphosphatemia (OR = 5.221, 95% CI: 2.747–9.924, p < 0.001) were identified as independent correlative factors associated with in-hospital mortality.

Hyperphosphatemia and severe hypophosphatemia upon admission were associated with increased in-hospital mortality in CAP inpatients.