Volume 21, Number 2—February 2015
Refining Historical Limits Method to Improve Disease Cluster Detection, New York City, New York, USA
|Explanation||No. signals produced by HLMoriginal||No. signals produced by HLMrefined|
|Attributable to an uncorrected bias toward signaling|
|Neighborhood disease count threshold too low||47†||0|
|Pending cases in current period||21||0|
|Increasing trends in baseline period||3||0|
|Total signals attributable to an uncorrected bias toward signaling
|Attributable to the correction of a bias against signaling|
|Confirmatory proportion higher in current period than in baseline period||9||0|
|Accounted for data accrual lags||0||17|
|Deleted outliers in baseline period||0||2|
|Adjusted for decreasing trends in baseline period||0||1|
|Total signals attributable to the correction of a bias against signaling
|Not attributable to any known systematic bias
*HLM, historical limits method; HLMoriginal, method as originally applied in NYC prior to May 20, 2013; HLMrefined, refined method applied starting May 20, 2013.
†These were excluded from the calculation of type I and type II error rates.
1Current affiliation: RTI International, Research Triangle Park, North Carolina, USA.
2Current affiliation: Colorado Department of Public Health and Environment, Denver, Colorado, USA.