Table 1.

Background characteristics of study population medical record research versus all hospitalized patients with main or side diagnosis varicella in 2003-2006

		Study population		All patients 2003-2006
		N	%	N	%	p-value
Age	0 year	94	31.8%	492	29.7%
	1-4 year	145	49.0%	760	45.8%
	≥5 year	57	19.3%	406	24.5%
Median		1	years	2	years	p = 0.103
Sex	Male	179	60.5%	931	56.2%	p = 0.181
	Female	117	39.5%	727	43.8%
Duration of admission	<1 day	45	15.3%	239	14.4%
	1-4 days	164	55.6%	875	52.8%
	≥5 days	86	29.2%	543	32.8%
Median		3.6	days	3.3	days	p = 0.658
Type of hospital	Academic	15	5.1%	185	11.2%	p = 0.001
	Other	281	94.9%	1473	88.8%
Type of diagnosis	Main	190	64.2%	1100	66.3%	p = 0.465
	Side	106	35.8%	558	33.7%
ICD-9 code*	052.0	2	1.1%	21	1.9%	p = 0.436
main diagnosis	052.1	11	5.8%	82	7.5%
	052.7	39	20.5%	261	23.7%
	052.8	16	8.4%	66	6.0%
	052.9	122	64.2%	670	60.9%
ICD-9 code*	052.0	0	0.0%	1	0.2%	p = 0.489
side diagnosis	052.1	0	0.0%	7	1.3%
	052.7	12	11.3%	72	12.9%
	052.8	1	0.9%	17	3.0%
	052.9	93	87.7%	461	82.6%
Total		296	100.0%	1658	100.0%

* ICD-9 code: 052.0 = postvaricella encephalitis, 052.1 = varicella (hemorrhagic) pneumonitis, 052.7 = varicella with other specified complications, 052.8 = varicella with unspecified complication, 052.9 = varicella without complication