- Kearney N, et al. Systemic immune inflammation index as a predictor of systemic inflammatory burden and cardiovascular comorbidities in psoriasis. FC23, Psoriasis from Gene to Clinic 2021, 9–11 December.
“The SII index is a simple calculation of neutrophils multiplied by platelets divided by lymphocytes,” Dr Niamh Kearney (St. Vincents University Hospital, Republic of Ireland) explained1. This index has been proven to be a promising prognostic indicator in various diseases, such as cancer, COVID-19, and cardiovascular disease. “In multiple cancers, a worse prognosis has been shown in patients with positive SII index,” Dr Kearny said.
Previous data has shown that it may be an additional diagnostic measure for prognosis and disease severity. Severe psoriasis is associated with a distinct risk elevation for cardiovascular events and death. With their study, Dr Kearny and her team wanted to assess whether SII index is increased in psoriasis, particularly in psoriasis patients with cardiovascular comorbidities. They also aimed to quantify the SII index in psoriasis and stratify it by the presence of diabetes, hypertension, dyslipidaemia, and coronary artery disease. In their retrospective cohort study, they analysed electronic and physical records from specialty psoriasis clinics.
“We looked at demographics, treatments, full blood count, and C-reactive protein results,” Dr Kearney explained. Patients on methotrexate were excluded from the study. The analysis included data from 73 patients. The majority of participants were on a biologic, and most of them were smokers. Dyslipidaemia was the most common comorbidity prevalent in 12.3% of patients, followed by hypertension in 11% of patients. The mean CRP for patients with cardiovascular comorbidities was 5.01mg/L compared with 3.53mg/L without co-morbidities (P=0.046).
The researchers found a modest correlation between the CRP concentrations and the SII index (r=0.530; P<0.001), and a weak significant correlation between the Psoriasis Area and Severity Index (PASI) and the SII index (r=0.299; P=0.011). However, no difference was observed in smokers, ex-smokers, and never smokers. Psoriasis patients with comorbidity had an SII index of 859.74 compared with 612.04 (P=0.014) in patients without comorbidity. In the individual comorbidity analysis, only hypertension was associated with a higher CRP of 7.4mg/L (P<0.001) and an SII index of 1038.05 (P=0.004).
The limitations of the study were the small number of patients with comorbidities and the lack of imaging data to confirm the association. Despite this, the authors think that the SII index might have a role in risk stratification for primary and secondary prevention in psoriasis patients.