Positive Fecal Immunochemistry Test May Increase Risk of Psoriasis

The fecal immunochemistry test (FIT) may be a predictive instrument in distinguishing risk of psoriasis development and potentially other chronic inflammatory skin diseases, according to study findings published in Dermatology.

Typically used as a biomarker to screen for colorectal cancer (CRC), fecal occult blood tests such as the FIT have been indicated as an effective, high sensitivity, low cost, and convenient approach that uses antibodies against human hemoglobin (Hb) to estimate the fecal Hb concentration.

Although a positive FIT result signifies a high risk of having or developing CRC, researchers note that the concentration of Hb in feces could be predictive of gut inflammation independent of CRC. With associations having been previously reported in regards to FIT-positive tests and endoscopic inflammation in patients with Crohn’s disease and ulcerative colitis, they sought to assess whether the screening test could also distinguish risk of psoriasis, a chronic inflammatory skin disease characterized by inflammatory reactions, and immune and vascular abnormalities.

“A correlation between psoriasis and gastrointestinal disorders, particularly inflammatory bowel disease, has been frequently reported, and several studies have suggested a causal link between psoriasis and gut inflammation,” noted the study authors. “Until now, the relationship between occult blood in feces and skin disease has not been explored in detail.”

Researchers conducted a retrospective nationwide population-based study of data derived from the South Korean National Health Insurance System to assess the link between FIT results and risk of psoriasis. In the study, 1,395,147 individuals aged 50 and older underwent health examinations from January 2009 to December 2012 and were followed up until the end of 2017.

The results of FITs were categorized as negative or positive according to the cutoff points of the test kits, with the primary outcome examining newly diagnosed patients with psoriasis and a separate subgroup analysis assessing incidence of psoriasis according to age, sex, body mass index (BMI), hypertension, diabetes, and dyslipidemia.

Of the study cohort, 204,180 patients (14.6%) reported positive FIT results during a median follow-up period of 6.68 years. These patients were indicated to be more likely older, male, current smokers, and heavy drinkers, as well as have a greater likelihood of comorbidities including hypertension, diabetes, dyslipidemia, and metabolic syndrome, compared with FIT-negative counterparts.

Compared with the FIT-negative group, patients reporting positive FIT results exhibited a higher incidence of psoriasis per 1000 person-years after the median follow-up period (3.76 vs 4.14).

Furthermore, the probability of psoriasis increased in proportion to the number of positive FIT results (log-rank test, P < .0001). After adjusting for age, sex, BMI, smoking, alcohol consumption, regular exercise, hypertension, diabetes, and dyslipidemia, findings of the multivariable-adjusted model showed significant risks of psoriasis development after one positive FIT result (adjusted HR [aHR], 1.029; 95% CI, 0.997-1.061), 2 positive results (aHR, 1.118; 95% CI, 1.04-1.201) and 3 positive results (aHR, 1.342; 95% CI, 1.157-1.557).

“Individuals with a positive FIT result are at risk of not only colorectal neoplasia but also of chronic inflammatory skin diseases,” concluded researchers. “Further study is needed to evaluate the causality of that relationship.”

Reference

Lee HJ, Han K, Soh H, et al. Occult blood in feces is associated with increased risk of psoriasis. Dermatology. Published online September 16, 2021. doi:10.1159/000518625