Table 1

Sensitivity and specificity by time since symptom onset6

SensitivitySpecificity
Days 1-7Days 8-14Days 15-21Days 22-35Days >35All time points
IgG*29.7% (22.1-38.6)66.5% (57.9-74.2)88.2% (83.5-91.8)80.3% (72.4-86.4)86.7% (79.6-91.7)99.1% (98.3-99.6)
IgM23.2% (14.9-34.2)58.4% (45.5-70.3)75.4% (64.3-83.8)68.1% (55.0-78.9)53.9% (38.4-68.6)98.7% (97.4-99.3)
IgA28.4% (0.9-94.3)78.1% (9.5-99.2)98.7% (39.0-100)98.7% (91.9-99.8)100% (85.2-100)
IgG or IgM*30.1% (21.4-40.7)72.2% (63.5-79.5)91.4% (87.0-94.4)96.0% (90.6-98.3)77.7% (66.0-86.2)98.7% (97.2-99.4)
  • * The main tests currently used in the NHS in the UK are the Abbott SARS-CoV-2 assay which detects IgG and the Roche Elecsys assay which detects both IgM and IgG