Epidemiol Health.  2012;34:e2012006.

Estimation of the Frequency of Intravenous Drug Users in Hamadan City, Iran, Using the Capture-recapture Method

Affiliations
  • 1Department of Epidemiology & Biostatistics, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran.
  • 2Research Center for Health Sciences, Department of Epidemiology & Biostatistics, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran. poorolajal@umsha.ac.ir
  • 3Department of Community Medicine, School of Medicine, Kurdistan University of Medical Sciences, Kurdistan, Iran.
  • 4Center for Disease Control & Prevention, Vice-chancellor of Health Services, Hamadan University of Medical Sciences, Hamadan, Iran.

Abstract


OBJECTIVES
The number of illicit drug users is prone to underestimation. This study aimed to use the capture-recapture method as a statistical procedure for measuring the prevalence of intravenous drug users (IDUs) by estimating the number of unknown IDUs not registered by any of the registry centers.
METHODS
This study was conducted in Hamadan City, the west of Iran, in 2012. Three incomplete data sources of IDUs, with partial overlapping data, were assessed including: (a) Volunteer Counseling and Testing Centers (VCTCs); (b) Drop in Centers (DICs); and (c) Outreach Teams (ORTs). A log-linear model was applied for the analysis of three-sample capture-recapture results. Two information criteria were used for model selection including Akaike's Information Criterion and the Bayesian Information Criterion.
RESULTS
Out of 1,478 IDUs registered by three centers, 48% were identified by VCTCs, 32% by DICs, and 20% by ORTs. After exclusion of duplicates, 1,369 IDUs remained. According to our findings, there were 9,964 (95% CI, 6,088 to 17,636) IDUs not identified by any of the centers. Hence, the real number of IDUs is expected to be 11,333. Based on these findings, the overall completeness of the three data sources was around 12% (95% CI, 7% to 18%).
CONCLUSION
There was a considerable number of IDUs not identified by any of the centers. Although the capture-recapture method is a useful and practical approach for estimating unknown populations, due to the assumptions and limitations of the method, the results must be interpreted with caution.

Keyword

Capture-recapture; Log-linear models; Poisson regression; Intravenous drug users; Iran

MeSH Terms

Counseling
Dacarbazine
Drug Users
Humans
Iran
Linear Models
Prevalence
Information Storage and Retrieval
Dacarbazine
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