Table 2. Univariate and multivariate logistic regression analyses of odds ratios for uncomplicated and complicated appendicitis (vs. normal and mild appendicitis).

	Study group (2020)				Control group (2019)
	Univariate		Multivariate		Univariate		Multivariate
	OR (95% CI)	P value	OR (95% CI)	P value	OR (95% CI)	P value	OR (95% CI)	P value
Bi-week interval (Jan 1–Jan 14)*		0.389		0.379		0.616		0.660
Jan 15–Jan 28, bi-week 2	3.25 (0.81–13.03)	0.096	5.81 (1.18–28.59)	0.030	2.81 (0.42–18.74)	0.285	6.38 (0.75–54.14)	0.090
Jan 29–Feb 11, bi-week 3	2.50 (0.36–17.32)	0.353	3.51 (0.41–29.79)	0.250	0.75 (0.15–3.83)	0.729	1.22 (0.18–8.32)	0.838
Feb 12–Feb 25, bi-week 4	3.75 (0.59–23.87)	0.162	7.18 (0.91–56.43)	0.061	0.75 (0.15–3.83)	0.729	1.51 (0.24–9.65)	0.665
Feb 26–Mar 10, bi-week 5#	10.00 (1.03–97.50)	0.048	12.63 (1.07–149)	0.044	0.47 (0.10–2.18)	0.335	0.60 (0.10–3.61)	0.579
Mar 11–Mar 24, bi-week 6#	1.67 (0.29–9.71)	0.570	1.13 (0.16–8.02)	0.906	0.87 (0.18–4.34)	0.870	1.71 (0.27–10.79)	0.569
Mar 25–Apr 7, bi-week 7#	1.56 (0.31–7.82)	0.587	2.66 (0.43–16.29)	0.291	0.47 (0.07–3.04)	0.427	0.79 (0.09–7.26)	0.837
Apr 8–Apr 21, bi-week 8#	11.25 (1.17–108)	0.036	9.46 (0.80–111.99)	0.075	0.55 (0.12–2.47)	0.433	1.33 (0.23–7.62)	0.747
Apr 22–May 5, bi-week 9#	3.00 (0.74–12.13)	0.123	4.51 (0.86–23.79)	0.076	2.50 (0.37–16.89)	0.347	2.29 (0.27–19.6)	0.449
May 6–May 19, bi-week 10#	2.92 (0.57–15.05)	0.201	5.80 (0.87–38.67)	0.069	1.13 (0.24–5.37)	0.883	2.62 (0.44–15.75)	0.293
May 20–June 2, bi-week 11#	1.75 (0.40–7.66)	0.458	3.84 (0.72–20.43)	0.115	0.87 (0.18–4.34)	0.870	1.71 (0.27–10.95)	0.571
June 3–June 16, bi-week 12#	10.00 (1.76–56.93)	0.009	13.46 (1.98–91.56)	0.008	1.87 (0.34–10.46)	0.474	5.02 (0.68–36.89)	0.113
June 17–June 30, bi-week 13#	3.13 (0.47–20.58)	0.236	4.25 (0.53–34.10)	0.173	1.87 (0.38–9.20)	0.438	2.92 (0.47–18.11)	0.251

OR: Odds ratio, CI: Confidence interval;

*: Interval in the parentheses indicate reference group; estimates were derived after controlling age, sex, comorbidity and surgery type;

^#: Add 1 day to each date after February 28 in the control group.