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Table 4 Estimated waxing and waning of IgA and IgG levels between diagnostic parameters

From: Sensitivity and specificity of single IgA and IgG antibody concentrations for early diagnosis of pertussis in adults: an evaluation for outbreak management in public health practice

Variable IgA IgG
Laboratory detection limit 5 U/ml 5 U/ml
100% sensitivity level in the 46 pertussis cases 24 U/ml 27 U/ml
90% specificity level in 4275 external controls 24 U/ml 27 U/ml
99% specificity level in 4275 external controls 74 U/ml 90 U/ml
GMC of the highest level obtained in week 9 and 12 of pertussis cases with at least 4-fold increase or decrease between week 9, 13 and 60 of the epidemic 229 U/ml
(n = 28 levels)
406 U/ml
(n = 49 levels)
Average speed of significant increase 16.0 U/ml/day
(n = 11 level pairs)
14.7 U/ml/day
(n = 9 level pairs)
Average speed of significant decrease 1.0 U/ml/day
(n = 18 level pairs)
2.9 U/ml/day
(n = 46 level pairs)
Mean time to increase from detection limit to 100% sensitivity level 1.2 days 1.5 days
Mean time to increase from detection limit to 99% specificity level 4.3 days 5.8 days
Mean time to increase from detection limit to GMC 14.0 days 27.3 days
Mean time to increase from 99% specificity level to GMC 9.8 days 21.5 days
Mean time to decrease from GMC to 99% specificity level 156.0 days 109.0 days
Mean time spent above 99% specificity level 165.8 days
(5.5 month)
130.5 days
(4.3 month)
Mean time to decrease from 99% specificity level to 100% sensitivity level 50.0 days 21.7 days
Total time spent going up and down between detection limit and GMC 238.0 days 165.6 days
Total time spent going up and down between 100% sensitivity level and GMC 217.8 days
(7.2 months)
156.5 days
(5.1 months)