Triggering Interventions for Flu: The ALERT Algorithm

Presentation made at the International Society for Disease Surveillance conference describing the ALERT algorithm, a method for predicting the onset of influenza season.

Transcript

1. Triggering Interventions for Flu: The ALERT Algorithm Nicholas G Reich Department of Biostatistics and Epidemiology University of Massachusetts - Amherst 10 Dec 2015 :: ISDS :: Denver, CO @reichlab http://reichlab.github.io
2. Anecdote: triggering the ResPECT Study intervention period in 2012-2013
3. The ResPECT Study Cluster-randomized clinical trial comparing N95 respirators vs. surgical masks at preventing respiratory infections in healthcare workers.
4. How to decide when to start the ResPECT study each season? 12 week “active” study period, ideally covering the peak flu season
5. 0 20 40 60 80 100 120 ODEïFRQILrPHG)OX$FDVHV 200 300 ILrPHG)OX$FDVHV Johns Hopkins Hospital &KLOGUHQ·V+RVSLWDO&RORUDGR 0 20 40 60 80 100 120 ODEïFRQILrPHG)OX$FDVHV 0 100 200 300 ODEïFRQILrPHG)OX$FDVHV 2002 2003 2004 2005 2006 2007 2008 2009 2010 Johns Hopkins Hospital &KLOGUHQ·V+RVSLWDO&RORUDGR Data from one ResPECT site: Johns Hopkins
6. Johns Hopkins Hospital lab-confirmed Influenza A cases
7. the “ALERT threshold” based on past data, set to 3 cases
8. week ending Nov 3 has 3 cases (we receive data on Nov 6)
9. Recommended start date: Nov 19
12. More generally: how to predict when flu season is starting? Literally, a $75,000 question, according to the CDC.
13. Why predict the flu? • For clinical trials, to time interventions.
 • In hospitals, to 
 - start target screening for flu antiviral use,
 - limit patient visitation, 
 - increase mandatory PPE usage.
 • For public health agencies, to determine the best timing for seasonal risk communication. “Predictions that give rise to actionable items that would not otherwise occur are important.” - Jay Varma, NYC DOHMH
14. The Above Local Elevated Respiratory illness Threshold Algorithm Reich et al, Clinical Infectious Diseases, 2015. http://tiny.cc/alertapp
15. Data Results Choice of threshold 0 20 40 60 80 100 120 ODEïFRQILrPHG)OX$FDVHV 0 100 200 300 ODEïFRQILrPHG)OX$FDVHV 2002 2003 2004 2005 2006 2007 2008 2009 2010 Johns Hopkins Hospital &KLOGUHQ·V+RVSLWDO&RORUDGR How ALERT works
16. Data Results Choice of threshold How ALERT works Median   dura*on Percent  of  cases  captured Peaks  captured Mean  weeks       <  threshold Mean  dura*on   difference Threshold median min max % %  +/-­‐  2   1 18 96.9 0 99.8 70 70 3.7 3.7 2 18 97.4 61.3 99.4 90 90 2.9 5.1 3 15.5 95.6 58 98.7 90 90 1.8 1.8 4 14.5 94 57.3 98.7 90 80 2 0.8 5 13 91.8 57.3 96.3 90 80 2.2 -­‐0.3 6 12.5 90.3 57.3 96.2 90 80 2.6 -­‐0.9 7 12 86.4 47.7 94.9 80 80 2.7 -­‐1.4 8 11 82.6 47.7 94.9 80 80 3 -­‐2.1 9 10.5 82.6 0 94.9 80 60 2.2 -­‐2.44 10 9 76.8 0 94.9 70 60 2.2 -­‐3.11
17. Data Results Choice of threshold How ALERT works Median   dura*on Percent  of  cases  captured Peaks  captured Mean  weeks       <  threshold Mean  dura*on   difference Threshold median minimu m maximu m % %  +/-­‐  2   1 18 96.9 0 99.8 70 70 3.7 3.7 2 18 97.4 61.3 99.4 90 90 2.9 5.1 3 15.5 95.6 58 98.7 90 90 1.8 1.8 4 14.5 94 57.3 98.7 90 80 2 0.8 5 13 91.8 57.3 96.3 90 80 2.2 -­‐0.3 6 12.5 90.3 57.3 96.2 90 80 2.6 -­‐0.9 7 12 86.4 47.7 94.9 80 80 2.7 -­‐1.4 8 11 82.6 47.7 94.9 80 80 3 -­‐2.1 9 10.5 82.6 0 94.9 80 60 2.2 -­‐2.44 10 9 76.8 0 94.9 70 60 2.2 -­‐3.11
18. Data Results Choice of threshold How ALERT works apply ALERT threshold to real-time data
19. What ALERT is • Threshold-based algorithm for surveillance data to give early warning signal for epidemic onset. • Simple method with cross-validated performance assessment. • A free online tool for hospital epidemiologists and public health officials. • Open-source, “beta” software (R package).
22. What ALERT is not • A statistical prediction model. (not yet…) • Generalizable for non-seasonal data. • A method for detecting outbreaks of emerging pathogens.
23. – statistical proverb “The plural of anecdote is not data.”
24. Region (CDC #) ResPECT Site ALERT Threshold start date/ season % of Flu A cases captured in 12 weeks Northeast (2) NYC VA 19 12/3/2012 94% 12/16/2013 76% 12/15/2014 90% Mid-Atlantic (3) JHU/DC VA 3 11/19/2012 91% 12/30/2013 90% 12/8/2014 95% Southwest (8) CHCO/DH 3 12/3/2012 87% 12/2/2013 93% 12/1/2014 97% South (6) Houston VA 5 11/11/2013 90% Data and Results
25. The future of ALERT [statistics] 
 Incorporate non-parametric prediction model. [epidemiology] 
 Apply ALERT to other seasonal diseases. [software] 
 Continue development and support of web applet and open-source R package.
26. Stephen A Lauer The ResPECT Study team Acknowledgments Alexandria C Brown Data collection teams/labs CHCO, NYC DOHMH, JHH, Houston
27. Thanks! ! http://tiny.cc/alertapp