Background: Chronic glycaemia (i.e., known diabetes or prediabetes) and acute glycaemia (i.e., elevated admission plasma (p)-glucose) are common in community-acquired pneumonia (CAP). C-reactive protein (CRP) is used to guide CAP treatment. A positive association between admission p-glucose and CRP levels during CAP has been observed. However, the association between prediabetes, unknown diabetes, and acute-on-chronic glycaemia and CRP levels during admission and between CRP levels and insulin resistance in CAP are unknown.

Objectives: To investigate associations 1) between chronic, acute, and acute-on-chronic glycaemia and CRP levels and  2) between admission CRP levels and insulin resistance in CAP.

Methods: In a prospective cohort study of adults with CAP, repeated-measures linear mixed model analyses were used to model the association between chronic, acute and acute-on-chronic glycaemia (i.e, difference between admission p-glucose and HbA1c-derived average p-glucose)  and CRP levels until admission day 3. Insulin resistance was estimated with the homeostasis model assessment of insulin resistance (HOMA-IR). The association between admission CRP levels and HOMA2-IR was modelled with linear regression. 

Results: Among 540 patients, there was no association between chronic, acute, or acute-on-chronic glycaemia and CRP levels.  Every 50 mg/L increase in admission CRP was associated with a 6 % (95% CI, 1-12) higher HOMA-IR.

Conclusion:  Chronic, acute, or acute-on-chronic glycaemia was not associated with CRP levels during admission in patients with CAP. The admission CRP level was positively associated with HOMA-IR.