Strong site-specific association of pharyngeal cultures with the onset of psoriatic arthritis and psoriasis, regardless of pathogen.

OBJECTIVES: The objective of this study was to evaluate any association between culture site / culture result / pathogen and incident PsA or psoriasis. METHODS: Records of all samples sent for culture from a large population during a 3-year period were linked with nationwide registry data on diagnoses and death over a 15-year period. The main outcomes of interest were incident diagnoses of PsA and psoriasis, defined by International Classification of Diseases (ICD) codes. The effect of culture site, culture result (positive vs negative), and pathogen (Streptococcus vs negative culture) on the risk of developing PsA and psoriasis was calculated using Cox proportional hazards models adjusted for age and gender. RESULTS: A total of 313 235 bacterial cultures from 128 982 individuals were analysed. Comparing individuals with pharyngeal cultures to those with urine cultures, the hazard ratio for incident PsA was 8.78 [95% confidence interval (CI) 3.23, 23.91] and for incident psoriasis it was 8.00 (95% CI 5.28, 12.12). Most of the risk was concentrated in the first 50 days after the culture date. Increased risk was also found when comparing individuals with cultures from the pharynx with those with cultures from the nasopharynx and blood. An association with streptococci was not found, neither in the pharynx nor at any other site. A positive bacterial culture from any site was associated with reduced risk for both PsA and psoriasis. CONCLUSION: There is a strong site-specific association between pharyngeal culture samples and an increased risk of PsA and psoriasis, regardless of the pathogen. This may indicate that the site of infection, rather than the pathogen, is associated with increased risk.

Risk Factors for Diagnosis of Psoriatic Arthritis, Psoriasis, Rheumatoid Arthritis, and Ankylosing Spondylitis: A Set of Parallel Case-control Studies.

OBJECTIVE: To compare potential risk factors for the diagnosis of psoriatic arthritis (PsA), psoriasis (PsO), rheumatoid arthritis (RA), and ankylosing spondylitis (AS). METHODS: Four parallel case-control studies were conducted within The Health Improvement Network using data between 1994 and 2015. Patients with PsA, PsO, RA, or AS were identified using validated code lists and matched to controls on age, sex, practice, and year. Risk factors were selected in the time prior to diagnosis. Multivariable logistic regression models were constructed for each disease using automated stepwise regression to test potential risk factors. RESULTS: Patients with incident PsA (n = 7594), PsO (n = 111,375), RA (n = 28,341), and AS (n = 3253) were identified and matched to 75,930, 1,113,345, 283,226, and 32,530 controls, respectively. Median diagnosis age was 48 (IQR 38-59), 43 (IQR 28-60), 60 (IQR 48-71), and 41 (IQR 32-54) years, respectively. In multivariable models, there were some shared and some differing risk factors across all 4 diseases: PsA was associated with obesity, pharyngitis, and skin infections; PsA and PsO were associated with obesity and moderate alcohol intake; PsA and AS were associated with uveitis; and PsA and RA were associated with preceding gout. Both RA and AS were associated with current smoking, former moderate drinking, anemia, osteoporosis, and inflammatory bowel disease. All shared former or current smoking as a risk factor; statin use was inversely associated with all 4 diseases. CONCLUSION: Shared and different risk factors for PsA, PsO, RA, and AS were identified. Statin use was inversely associated with all 4 conditions.

Infections and the risk of psoriatic arthritis among psoriasis patients: a systematic review.

Psoriasis and psoriatic arthritis (PsA) are related inflammatory diseases with some shared genetic and environmental risk factors. It has been suggested that environmental factors, including infections, can trigger the development of PsA among psoriasis patients. The aim of this review was to systematically examine available data evaluating the effect of infections on the risk of developing PsA. A systematic search of the Cochrane Library, PubMed, Scopus, and Web of Science was conducted on March 16 2017, in accordance with the PRISMA statement. The following search terms were used along with "psoriatic arthritis": "infections", "risk", "bacteria", and "virus". Abstracts were reviewed and publications meeting the following criteria included: (1) Observational studies on psoriasis and PsA patients, including case-control, cohort, or ecologic studies and (2) presenting original data on the association between infections and PsA. The protocol for this systematic review was registered on PROSPERO (ID: 79432). Twenty-seven original studies presenting data on infections among PsA patients were included. Eight studies showed a statistically significant association between infections and PsA. In addition, seven studies reported mixed result with some statistically significant associations and five studies did not find statistically significant associations. This included studies of bacterial as well as viral pathogens and those of infections in general. The remaining seven studies lacked data to determine statistical significance. Out of all included studies, the total number of included patients was 933 PsA patients and 1611 controls. While the studies summarized did not all provide evidence supporting an association between infections and PsA certain trends emerged. The available data are inconsistent and further studies are needed to verify or refute this purported association. In particular, laryngeal infections and infections involving streptococci should be studied more carefully.