Using a Novel Inflammation Index to Predict Psoriasis Onset

The novel systemic-immune inflammation index (SII) can be used to predict the onset of psoriasis.

Systemic-immune inflammation index (SII), a novel measure based on neutrophil, platelet, and lymphocyte counts utilized in predicting disease progression in cancer, can be used for predicting the onset of psoriasis, according to a new study.

Researchers at a university hospital in Turkey performed a study comparing patients with psoriasis with an age- and gender-matched control group of those with other noninflammatory dermatologic diseases to determine if SII could play a role in the management of the skin disease.

In the study, published this month in the International Journal of Clinical Practice, researchers found that patients with psoriasis had significantly higher SII values (P <.05), indicating the index can be used to predict psoriasis activation.

The study further evaluated patients in association with another measure called psoriasis area severity index (PASI) to measure disease severity. Four body parts—head, arms, trunk, and legs—were evaluated for PASI score based on the percentage of affected skin area. Severity was rated through 3 clinical signs: skin redness, localized hardening of the skin, and peeling.

Patients at or over the 50th percentile in the index, as well as patients whose nails and genital areas were affected, also had significantly higher SII values (P <.05) than those in the control group. Those with scalp and joint psoriasis did not have higher SII values.

Psoriasis is a chronic inflammatory skin disease affecting 0.5% to 11.4% of the world’s adult population. The authors wanted to evaluate the index in relation to psoriasis because they suspected its inclusion of 3 main parameters of complete blood cell count might provide a level of precision in predicting the disease’s progression. Currently used laboratory tests are insufficient for that purpose, they said.

“SII has not been used for the evaluation of psoriasis activation before and in our opinion it may be beneficial for physicians who work in the field,” the authors wrote.

Given the challenge of accurate psoriasis prognosis, however, they recommended that SII be used in conjunction with physical examination and conservative laboratory tests.

The study evaluated 71 patients with psoriasis who were admitted to a dermatology outpatient clinic from 2017-2019 against a control group of 70 patients.

Other indices have been assessed in the literature—red cell distribution width, mean platelet volume, neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio were the most commonly used. However, the authors said, factors such as anemia, infection, and other inflammatory markers may affect those indices. Furthermore, their utility has not been validated through high-quality studies.

The authors contended that the strength of SII over NLR is the inclusion of platelet counts. Platelets play a crucial role in immune-mediated processes such as releasing antimicrobial proteins and producing inflammatory cytokines. They also play a role in clotting, the process of preventing clots from growing, and the physiological process through which new blood vessels form from pre-existing vessels.


Dincer Rota D, Tanacan E. The utility of systemic-immune inflammation index for predicting the disease activation in patients with psoriasis. Int J Clin Pract. 2021;e14101. Published online February 22, 2021. doi:10.1111/ijcp.14101.