Table 3.

Risk ratios (RR) to assess associations between patient and surgery characteristics and need of reoperation

			Re-operation		Risk ratio
Patient characteristics		N	N%	%	RR	95% CI	p-value
Age, years	≤ 26	43	12	27.9	Ref.*
	≥ 27	40	11	27.5	0.99	0.49—1.98	1.00
BMI, kg/m2	< 25.0	29	7	24.1	Ref
	25.0–29.9	43	14	32.6	1.35	0.62—2.93	0.60
	≥ 30.0	11	2	18.2	0.75	0.18—3.09	1.00
Gender	male	65	17	26.2	Ref
	female	18	6	33.3	1.27	0.59—2.75	0.56
ASA	1	53	14	26.4	Ref
	2–3	30	9	30.0	1.14	0.56—2.30	0.80
Alcohol	Non-drinker	39	13	33.3	Ref
	Drinker	44	10	22.7	0.68	0.34—1.38	0.30
Smoking	Non-smoker	57	15	26.3	Ref
	Smoker	26	8	30.8	1.17	0.57—2.41	0.79
Diabetes	Non-diabetic	79	21	26.6	Ref
	Diabetic	4	2	50.0	1.88	0.66—5.36	0.31
Acute abscess before	No	24	7	29.2	Ref
laser treatment	Yes	59	16	27.1	0.93	0.44—1.97	1.00
Surgery characteristics
Pre and/or postop hair	No	61	14	23.0	Ref
depilation	Yes	22	9	40.9	1.78	0.90—3.52	0.16
Type of PSD	Primary	70	14	20.0	Ref
	Recurrent	13	9	69.2	3.46	1.91—6.26	< 0.001
Spillage of pus	No	68	15	22.1	Ref
during operation	Yes	15	8	53.3	2.42	1.26—4.64	0.02
Number of sinus openings	1	15	5	33.3	Ref
	2	46	11	23.9	0.72	0.30—1.73	0.51
	3–5	22	7	31.8	0.95	0.37—2.45	1.00
Surgeon	Senior	71	19	26.8	Ref
	Junior	12	4	33.3	1.25	0.51—3.03	0.73

^* Ref. = reference group