title: Association between Giardia and arthritis or joint pain in a large health insurance cohort: could it be reactive arthritis?
abstract: This study aimed to assess the association between giardiasis and subsequent development of arthritis or joint pain using a retrospective cohort of individuals from a large administrative claims database in the United States. Using 2006-2010 data from MarketScan Commercial Claims and Encounters, we conducted a retrospective cohort study in people with an ICD-9-CM code for giardiasis (n = 3301) and persons without giardiasis (n = 14 612) individually matched on age, sex, and enrolment length. We used conditional logistic regression to model the association between giardiasis and arthritis or joint pain documented in the 6 months following initial giardiasis diagnosis or index date for matched controls. After adjusting for healthcare utilization rate, giardiasis was associated with a 51% increase in claims for arthritis or joint pain (odds ratio 1·51, 95% confidence interval 1·26-1·80). In age- and sex-stratified adjusted analyses, the association remained significant across all subgroups (age 0-19 years, age 20-64 years, males, and females). Findings from this study lend epidemiological support for the association between giardiasis and subsequent development of arthritis. Reactive arthritis might occur more frequently than has been reported in the literature. Further research is necessary to determine the mechanisms by which giardiasis could lead to arthritis.
authors.affiliation: Department of Global and Community Health,College of Health and Human Services,George Mason University,Fairfax,VA,USA.
authors.forename: J E
authors.initials: JE
authors.lastname: Painter
authors.affiliation: Division of Foodborne , Waterborne, and Environmental Diseases,National Center for Emerging Zoonotic and Infectious Diseases, Centers for Disease Control and Prevention,Atlanta,GA,USA.
authors.forename: S A
authors.initials: SA
authors.lastname: Collier
authors.affiliation: Division of Foodborne , Waterborne, and Environmental Diseases,National Center for Emerging Zoonotic and Infectious Diseases, Centers for Disease Control and Prevention,Atlanta,GA,USA.
authors.forename: J W
authors.initials: JW
authors.lastname: Gargano
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D018771:Arthralgia / Q000453:epidemiology* / Q000209:etiology*; D016918:Arthritis, Reactive / Q000453:epidemiology* / Q000209:etiology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005873:Giardiasis / Q000150:complications*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D017678:Sex Distribution; D014481:United States / Q000453:epidemiology; D055815:Young Adult
keywords: 
                 Giardia
              ; Arthritis; commercial claims data; giardiasis; medical claims; post-infectious arthritis; reactive arthritis