Biology Reference
In-Depth Information
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Correlation coefficients cannot determine the thresholds for trigger-
ing an alert.
Correlation coefficients cannot be used to define a change or level
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that might be indicative of disease occurrence or an outbreak
(Suyama et al. 2003).
1.5 Data Timeliness and Accuracy
As outlined by Buckeridge and colleagues (2002), data sources that are chron-
ologically distant from diagnostic information are timely but not as specific
as data sources that are chronologically closer to diagnosis. However, there
is a trade-off between data timeliness and specificity/accuracy. For example,
OTC sales have the benefit of timeliness, but are not very specific. A rise in
sales of antidiarrheal remedies may be associated with an increase in the
incidence of diarrheal illness or may be unrelated, such as store specials
and sale items. It would be difficult to make a public health decision based
solely on increased OTC sales because it does not contain any patient-specific
data (Berger, Shiau, and Weintraub 2006). Therefore, the timeliness of a data
source is only valuable if the signal is accurate and specific enough to inform
public health decision making (Berger, Shiau, and Weintraub 2006).
Timely signals and alerts generated by surveillance activities may not
always correspond to an actual increase in disease. A system based on ED
chief complaints found that over the course of 277 days, 59 signals were inves-
tigated and found not to correspond to an outbreak of communicable disease
(Terry, Ostrowsky, and Huang 2004). A system implemented for the 2002
Olympic Games tracked emergency department presentations using real-
time surveillance (Gesteland et al. 2003). During the 2-month period of the
Olympics, the system's detection algorithms alerted twice, and neither of
these alarms corresponded to a real outbreak.
Timeliness provided
by a biosurveillance system can only be useful if a
process of aberration verification and investigation occurs and is supported
by and integrated into
the activities of the local health department on a sus-
tained
basis (Berger, Shiau, and Weintraub 2006).
1.6 Conclusions
Although in its infancy, the field of biosurveillance has been the subject of mul-
tiple studies and scientific debate. The main reason for investigating this sur-
veillance method is the promise of earlier outbreak detection. Timeliness is one
metric used to assess the potential of data sources for early outbreak detection.
