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Table 2 Minimum Hypothetical and Expected Observed Prevalence Ratio to Detect an Outbreak of Microcephaly if Zika Virus Infection Risk Doubles, by Sensitivity and Specificity of Microcephaly Case Detection

From: An assessment of public health surveillance of Zika virus infection and potentially associated outcomes in Latin America

Microcephaly TEM a(cm) Sensitivity (%) Specificity (%) Prevalence ratio
Hypothetical Expected Observed
All 0.24 85.1 99.4 2.00 1.06
0.42 77.6 98.8 2.00 1.04
0.71 91.2 97.2 2.00 1.03
Severe 0.24 81.9 99.9 24.00 1.48
0.42 75.0 99.9 27.50 1.43
0.71 65.9 99.6 39.50 1.33
  1. a TEM: Technical error of head circumference measurements. TEM = 0.71 came from Bhushan et al. (J Clin Epidemiol Vol. 44 (10):1027–1035, 1991), but values of sensitivity and specificity for all microcephaly were taken directly from their article, while those for severe were obtained by simulation. All other TEM values came from Onis (Acta Pædiatrica, 2006; Suppl 450:38–46) and were used to estimate sensitivity and specificity by simulation
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