Prevalence of heroin and methamphetamine male users in the northern Taiwan, 1999–2002: capture-recapture estimates

Table 2 Estimated numbers and prevalence of illegal drug users by year, Taoyuan County, Taiwan

	1999			2000			2001			2002
Variable	All^a	MeA^b	H^c	All	MeA	H	All	MeA	H	All	MeA	H
Captured users, resident of Taoyuan County
Prison only	2505	2294	306	2135	1834	301	1269	945	324	823	516	311
Hospital only	225	147	80	299	143	156	359	148	210	554	196	388
Overlap	42	33	24	53	31	36	30	11	23	44	16	36
Estimate of undetected users	13420	10219	1020	12045	8460	1304	15186	12715	2958	10362	6321	3352
Estimate of total users	16192	12693	1430	14532	10468	1797	16844	13819	3515	11783	7049	4087
Lower bound of 95% C.I.^d	12421	9485	1049	11463	7749	1385	12111	8071	2462	8998	4528	3079
Upper bound of 95% C.I.	21436	17368	2037	18649	14475	2400	23719	24309	5150	15593	11241	5528
Estimate of the prevalence^e	3.04%	2.38%	0.27%	2.65%	1.91%	0.33%	3.01%	2.47%	0.63%	2.07%	1.24%	0.72%
Lower bound of 95% C.I.	2.33%	1.78%	0.20%	2.09%	1.41%	0.25%	2.17%	1.44%	0.44%	1.58%	0.79%	0.54%
Upper bound of 95% C.I.	4.03%	3.26%	0.38%	3.41%	2.64%	0.44%	4.24%	4.35%	0.92%	2.74%	1.97%	0.97%

^aAny case who was involved in the use of either methamphetamine or heroin.
^bAny case who was involved in the use of methamphetamine.
^cAny case who was involved in the use of heroin.
^dConfidence interval by using log-transformation
^eDuring the period 1999–2002, the annual statistics of male residents aged 15–54 in Taoyuan County were 532378, 547664, 558908, and 570034, respectively.

ISSN: 1471-2458