Table 4. Interaction effect on pyogenic liver abscess between splenectomy and other comorbidities.

Variable		n	Event	Person-years	Incidencea	Adjusted HRb (95% CI)
Splenectomy	Comorbidityc
No	No	49 400	93	345 670	0.27	1 (Reference)
No	Yes	21 455	169	112 128	1.51	5.01 (3.89–6.47)
Yes	No	12 350	91	61 082	1.49	5.84 (4.37–7.81)
Yes	Yes	5429	80	18 587	4.30	14.34 (10.61–19.39)

CI, confidence interval; HR, hazard ratio.

^aIncidence: per 1000 person-years.

^bAdjusted for age.

^cPatients with any examined comorbidities, including alcoholism, biliary stone, chronic kidney disease, chronic liver diseases and diabetes mellitus, were classified as the comorbidity group.

The interaction between splenectomy and comorbidities was significant (P value for interaction <0.001).