| Information component |
Pg 4 Health Summary – Indicator No. 27 |
| Subject category / domain(s) |
Health and ill health in our community |
| Indicator name (* Indicator title in health profile) |
Prevalence of Problem Drug Users by DAAT (*Drug misuse) |
| PHO with lead responsibility |
NWPHO |
| Date of PHO dataset creation |
May. ‘07 |
| Indicator definition |
Estimated Problem Drug Users (Crack & Opiates), Crude Rate, 15-64 Ages, 2004-05, persons |
| Geography |
England, GOR, Local Authority: Counties, County Districts, Metropolitan County Districts, Unitary Authorities, London Boroughs |
| Timeliness |
Every year. Time trend analysis is not appropriate. |
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Rationale:What this indicator purports to measure
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This indicator estimates the number of problem drug users (Crack & Opiates) in an area. |
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Rationale:Public Health Importance
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The indicator was chosen as the best available estimate of drug use prevalence in an area. |
| Rationale: Purpose behind the inclusion of the indicator |
To help monitor likely health care burden from drug misuse. |
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Rationale:Policy relevance
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| Interpretation: What a high / low level of indicator value means |
A high indicator value (red circle in health summary chart) represents a statistically significant higher estimate of problem (crack and opiates) drug users for that local authority when compared to the national value.A low indicator value (amber circle in health summary chart) represents a statistically significant lower estimate of problem (crack and opiates) drug users for that local authority when compared to the national value. Confidence Intervals for Top Tier Local authorities (Counties, MCDs, UAs, LBs) were taken from the HO published prevalence data but cannot currently be calculated for County Districts. Therefore interpretation of significance for County Districts cannot be made. |
| Interpretation: Potential for error due to type of measurement method |
The base estimates of the number of problem drug users were published by the Home Office and issues with the methods are outlined in the report (www.homeoffice.gov.uk/rds/pdfs06/rdsolr1606.pdf). A regression model uses number of users in treatment to disaggregate the County level estimates to County Districts. Treatment data is only available with postcode sector of residence which is not available for a large proportion of cases reported by DAATs, consequently the allocation of cases to LAs is likely to be less accurate for some areas than for others. |
| Interpretation: Potential for error due to bias and confounding |
The number of users in treatment will have impacted on the prevalence estimates published by the Home Office and the regression model which may introduce bias to the estimates. |
| Confidence Intervals: Definition and purpose |
A confidence interval is a range of values that is normally used to describe the uncertainty around a point estimate of a quantity, for example, a mortality rate. This uncertainty arises as factors influencing the indicator are subject to chance occurrences that are inherent in the world around us. These occurrences result in random fluctuations in the indicator value between different areas and time periods. In the case of indicators based on a sample of the population, uncertainty also arises from random differences between the sample and the population itself.The stated value should therefore be considered as only an estimate of the true or ‘underlying’ value. Confidence intervals quantify the uncertainty in this estimate and, generally speaking, describe how much different the point estimate could have been if the underlying conditions stayed the same, but chance had led to a different set of data. The wider is the confidence interval the greater is the uncertainty in the estimate.Confidence intervals are given with a stated probability level. In Health Profiles 2007 this is 95%, and so we say that there is a 95% probability that the interval covers the true value. The use of 95% is arbitrary but is conventional practice in medicine and public health. The confidence intervals have also been used to make comparisons against the national value. For this purpose the national value has been treated as an exact reference value rather than as an estimate and, under these conditions, the interval can be used to test whether the value is statistically significantly different to the national. If the interval includes the national value, the difference is not statistically significant and the value is shown on the health summary chart with a white symbol. If the interval does not include the national value, the difference is statistically significant and the value is shown on the health summary chart with a red or amber symbol depending on whether it is worse or better than the national value respectively. |
