Table 2.
Conditional probability for the diagnosis of SARS-CoV-2 infection depending on pre-test probability by clinical situation, age and unknown or close contact [20], presuming a sensitivity of 89% and a specificity of 99%, LR +/- 89/0.11 (RT-PCR)[5] and a sensitivity of 56% and a specificity of 99%, LR +/- 56/0.44 (Ag-RDT) [10].
| Asymptomatic | Odynophagia + nasal congestion | Odynophagia + nasal congestion + anosmia/ageusia | Odynophagia + nasal congestion + anosmia/ageusia + fever + body weakness | Asymptomatic | Odynophagia + nasal congestion | Odynophagia + nasal congestion + anosmia/ageusia | Odynophagia + nasal congestion + anosmia/ageusia + fever + body weakness | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Unknown contact | 20-30 years old | 60-70 years old | ||||||||||||||||||||
| Pre-test probability | 3% | 35% | 80% | 85% | 5% | 50% | 80% | 90% | ||||||||||||||
| RT-PCR | Ag-RDT | RT-PCR | Ag-RDT | RT-PCR | Ag-RDT | RT-PCR | Ag-RDT | RT-PCR | Ag-RDT | RT-PCR | Ag-RDT | RT-PCR | Ag-RDT | RT-PCR | Ag-RDT | |||||||
| Infection P (PPV) if positive (+) result | 74 (27-95) |
63 (17-93) |
98 (86-100) |
97 (79-100) |
99.7 (94-100) |
99.6 (91-100) |
99.8 (95-100) |
99.7 (92-100) |
82 (41-97) |
75 (29-95) |
99 (90-100) |
98 (85-100) |
99.7 (94-100) |
99.6 (91-100) |
99.9 (95-100) |
99.8 (93-100) |
||||||
| Infection P (1- NPV) if negative (-) result | 0.3 (0-4) |
1.4 (0.3-6) |
6 (2-14) |
19 (12-29) |
31 (17-49) |
64 (51-75) |
39 (22-58) |
72 (58-82) |
0.6 (0.1-5) |
2.3 (0.7-8) |
10 (4-21) |
31 (21-42) |
31 (17-49) |
64 (51-75) |
50 (30-70) |
80 (67-89) |
||||||
| Close contact | 20-30 years old | 60-70 years old | ||||||||||||||||||||
| Pre-test probability | 40% | 60% | 87% | >95% | 45% | 77% | 94% | >95% | ||||||||||||||
| RT-PCR | Ag-RDT | RT-PCR | Ag-RDT | RT-PCR | Ag-RDT | RT-PCR | Ag-RDT | RT-PCR | Ag-RDT | RT-PCR | Ag-RDT | RT-PCR | Ag-RDT | RT-PCR | Ag-RDT | |||||||
| Infection P (PPV) if positive (+) result | 98 (88-100) |
97 (81-100) |
99 (92-100) |
99 (88-100) |
99.8 (95-100) |
99.7 (92-100) |
99.9 (96-100) |
99.9 (93-100) |
99 (89-100) |
98 (83-100) |
99.7 (94-100) |
99.5 (91-100) |
99.9 (95-100) |
99.9 (93-100) |
99.9 (96-100) |
99.9 (93-100) |
||||||
| Infection P (1- NPV) if negative (-) result | 7 (3-16) |
23 (15-33) |
14 (7-27) |
40 (29-52) |
43 (25-63) |
75 (61-85) |
73 (47-89) |
91 (80-97) |
8 (3-18) |
27 (18-38) |
27 (15-44) |
60 (47-72) |
63 (40-82) |
87 (75-94) |
73 (47-89) |
91 (80-97) |
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P: probability; PPV: positive predictive value; NPV: negative predictive value. LR +/-: Positive/negative likelihood ratio. Post-test probability is expressed in % (95% CI).