Table 3 Specificity of reporting thresholds when used alone or in a serial approach.

From: Effective thresholds for reporting suspicions and improve early detection of avian influenza outbreaks in layer chickens

Thresholds

Specificity %

False alarm (FA) rate. Number FA/day X 1000 farms

Mortality

   Mortality % ≥0.5 (1 day)a

100.0

0.00 (0.00–0.27)

   Mortality % ≥0.25 (1 day)a

90.3

0.22 (0.05–0.65)

   Mortality % ≥0.25 (2 day)b

100.0

0.00 (0.00–0.27)

  Ratio >2.9b

71.0

0.79 (0.33–1.26)

  CUSUMb

35.5

2.25 (1.53–2.97)

  Mortality % >0.08/0.13b

87.1

0.39 (0.02–0.77)

Egg production

   Ratio production <0.94b

38.7

2.37 (1.59–3.15)

   CUSUMb

22.7

3.23 (2.25–4.22)

Serial use of thresholdsc

Ratio-mortality

   Mortality % >0.08/0.13

97.0

0.07 (0.00–0.41)

   CUSUM- egg

100.0

0.00 (0.00–0.27)

   Ratio production

97.0

0.07 (0.00–0.41)

CUSUM-mortality

  Mortality % >0.08/0.13

93.5

0.15 (0.02–0.53)

   CUSUM-egg

93.5

0.15 (0.02–0.53)

   Ratio production

96.8

0.07 (0.00–0.41)

  1. aAn alarm in triggered the first day the threshold is passed.
  2. bFor these thresholds an alarm is triggered when the threshold is passed for at least two consecutive days.
  3. cA screening threshold (Ratio-mortality or CUSUM-mortality) triggers an alarm when a threshold is passed for at least two consecutive days. The confirmation threshold needs to be passed for only one day following the alarm triggered by the screening.
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