Population-based studies have demonstrated that increased
retinal venular calibre is a risk factor for
cardiac disease,
cardiac events and
stroke. Venular dilatation also occurs with diabetes,
obesity,
dyslipidemia and
autoimmune disease where it is attributed to
inflammation. This study examined whether the
inflammation associated with
infections also affected microvascular calibre. Participants with
infections and CRP levels > 100 mg/L were recruited from the medical wards of a teaching hospital and assisted to complete a demographic and vascular risk factor questionnaire, and to undergo non-
mydriatic retinal photography (Canon CR5-45NM, Japan). They were then treated with appropriate
antibiotics, and underwent repeat
retinal imaging when their CRP levels had fallen to less than 100 mg/L.
Retinal images were examined for arteriole and venular calibre using validated semi-automated software based on Knudtson's modification of the Parr-Hubbard formula (IVAN, U Wisconsin). Differences in inflammatory markers and calibre were examined using the paired t-test for continuous variables. Determinants of calibre were calculated from multiple linear regression analysis. Forty-one participants with respiratory (27, 66%), urinary (6, 15%), skin (5, 12%), or miscellaneous (3, 7%)
infections were studied. After
antibiotic treatment, participants' mean CRP levels fell from 172.9 ± 68.4 mg/L to 42.2 ± 28.2 mg/L (p < 0.0001) and mean neutrophil counts fell from 9 ± 4 × 109/L to 6 ± 3 × 109/L (p < 0.0001). The participants' mean venular calibre (CRVE) decreased from 240.9 ± 26.9 MU to 233.4 ± 23.5 MU (p = 0.0017) but arteriolar calibre (CRAE) was unchanged (156.9 ± 15.2 MU and 156.2 ± 16.0 MU, p = 0.84). Thirteen additional participants with
infections had a CRP > 100 mg/L that persisted at review (199.2 ± 59.0 and 159.4 ± 40.7 mg/L, p = 0.055). Their CRAE and CRVE were not different before and after
antibiotic treatment (p = 0.96, p = 0.78). Hospital inpatients with severe
infections had
retinal venular calibre that decreased as their
infections resolved and CRP levels fell after
antibiotic treatment. The changes in venular calibre with intercurrent
infections may confound
retinal vascular assessments of, for example, blood pressure control and cardiac risk.