Abstract
Standardised sex-adjusted prevalence ratios (SSPRs) have not been published for any autoimmune diseases (ADs) in patients with Postural Orthostatic Tachycardia Syndrome (POTS), who are predominantly young females. We performed a systematic review according to PRISMA guidelines of POTS cohorts reporting the prevalence of at least one AD. Only four studies were found: two providing data on celiac disease; and two with data on 'any AD', Hashimoto's thyroiditis, rheumatoid arthritis, systemic lupus erythematosus (SLE), Sjögren's syndrome and celiac disease and (one study) antiphospholipid syndrome. All studies were assessed as being at high risk of bias for estimating AD prevalence in POTS patients, with under-reporting of ADs likely due to the lack of rigorous prospective screening for ADs. A literature search found a 'gold standard' general population (GP) comparator only for celiac disease in the United States, leading to a pooled SSPR in POTS patients of 2.75 with 95% confidence interval (1.06-4.40). The lack of recent high-quality studies on GP prevalence for the other ADs was noteworthy. Exploratory pooled SSPRs were calculated for 'any AD' and for the other five ADs using GP comparator data from a comprehensive review. All pooled SSPRs were greater than one and statistically significant, implying a higher prevalence of these ADs, and any AD, in POTS patients. The magnitude of the exploratory SSPRs was very large for SLE, Sjögren's syndrome and antiphospholipid syndrome, perhaps reflecting the use of non-gold standard GP comparators, which may underestimate AD prevalence. Further research in a large POTS cohort with an appropriately age- and sex-matched GP control group is recommended, to confirm the SSPR for celiac disease and to determine whether SLE, Sjogren's syndrome and antiphospholipid syndrome are indeed many times more prevalent in POTS patients than in the GP. The findings are consistent with POTS itself being an AD.