Table 2.

Association between giardiasis and subsequent documentation of arthritis or joint pain within 6 months of giardiasis index date^*, MarketScan commercial health insurance database, 2006–2010

	Unadjusted		Adjusted†
	OR	(95% CI)	OR	(95% CI)
Giardiasis	1·69	(1·42–2·00)	1·51	(1·26–1·80)
Medical claims for:
Smoking	1·49	(1·03–2·16)	—
Anxiety	2·49	(1·88–3·29)	—
Depression	1·63	(1·25–2·13)	—
Healthcare utilization rate quartile
1	1·00	(ref.)	1·00	(ref.)
2	1·41	(1·05–1·88)	1·34	(1·00–1·79)
3	2·08	(1·59–2·72)	1·97	(1·51–2·59)
4	2·67	(2·05–3·46)	2·40	(1·84–3·13)

OR, Odds ratio; CI, confidence interval; ref., referent.

^*The earliest record where a patient was given the ICD-9 code for giardiasis was considered their index date. Matched, unexposed persons (non-giardiasis cohort) were assigned an index date.

^†Adjusted for variables that change the risk ratio for giardiasis by >10% in preliminary logistic regression analyses.