Diabetes Status, c-Reactive Protein, and Insulin Resistance in Community-Acquired Pneumonia-A Prospective Cohort Study

Abstract

C-reactive protein (CRP) is commonly used to guide community-acquired pneumonia (CAP) treatment. A positive association between admission glucose and CRP levels has been observed in patients with CAP. The associations between prediabetes, unknown diabetes, acute-on-chronic hyperglycaemia, and CRP levels, and between admission CRP levels and insulin resistance (IR) in CAP, remain unexplored. This study investigated the associations firstly between chronic, acute, and acute-on-chronic hyperglycaemia and CRP levels, and secondly between admission CRP levels and IR in CAP. In a prospective cohort study of adults with CAP, the associations between chronic, acute, and acute-on-chronic hyperglycaemia (admission glucose minus HbA1c-derived average glucose) and CRP levels until admission day 3 were modelled with repeated-measures linear mixed models. IR was estimated with the homeostasis model assessment of IR (HOMA-IR). The association between admission CRP levels and HOMA-IR was modelled with linear regression. In 540 patients, no association between chronic, acute, or acute-on-chronic hyperglycaemia and CRP levels was found. In 266 patients, every 50 mg/L increase in admission CRP was associated with a 7% (95% CI 1-14%) higher HOMA-IR. In conclusion, our findings imply that hyperglycaemia does not influence CRP levels in patients with CAP, although admission CRP levels were positively associated with IR.

Keywords: acute hyperglycaemia; acute-on-chronic hyperglycaemia; c-reactive protein; chronic hyperglycaemia; community-acquired pneumonia; diabetes mellitus; insulin resistance.

Figure 1

Flow chart of patient enrolment. Abbreviations: p, plasma; HOMA-IR, homeostasis model assessment for insulin resistance; COVID-19, coronavirus disease 2019.

Figure 2

The figure shows the predicted values of geometric mean CRP with a 95% CI from admission until day 3 from linear, mixed models with age, sex, time, CURB-65 score, and corticosteroid treatment as fixed effects and patients as random effects. Predicted CRP values are stratified by chronic hyperglycaemia (A), acute hyperglycaemia (B), acute-on-chronic hyperglycaemia (C), and in-hospital glucocorticoid treatment (D). The p-value in each figure is from the analysis of variance of Type II multivariate Wald tests of fully adjusted linear mixed models for each predictor entered as a categorical variable (i.e., chronic hyperglycaemia groups, admission glucose groups, and glycaemic gap quartiles). The effect of glucocorticoid treatment was similar across the linear mixed models, and the p-value shown in (D) is from the model where chronic hyperglycaemia was the predictor.