TABLE 2.

Determination of the limit of detection of the QIAstat-Dx assay and comparison with the WHO-recommended PCR assay^a

Viral load and replicateb	QIAstat-Dx	E gene	RdRp gene
2000 cp/ml
Replicate 1	35.0	35.4	Negative
Replicate 2	35.6	35.4	Negative
Replicate 3	35.7	35.4	Negative
1,000 cp/ml
Replicate 1	35.1	33.6	Negative
Replicate 2	35.1	34.5	Negative
Replicate 3	35.1	34.7	Negative
Replicate 4	35.2	34.7	Negative
Replicate 5	35.4	35.0	Negative
Replicate 6	35.7	35.2	Negative
Replicate 7	35.7	35.9	Negative
Replicate 8	35.9	35.9	Negative
Replicate 9	36.7	36.2	Negative
Replicate 10	37.6	Negative	Negative
500 cp/ml
Replicate 1	36.8	34.3	Negative
Replicate 2	37.3	34.7	Negative
Replicate 3	37.6	36.4	Negative
Replicate 4	Negative	37.2	Negative
Replicate 5	Negative	Negative	Negative
250 cp/ml
Replicate 1	37.8	Negative
Replicate 2	Negative	Negative
125 cp/ml
Replicate 1	Negative	37.2
Replicate 2	Negative	Negative

^aThe limit of detection (LoD) is defined, according to the European Network of GMO Laboratories recommandations, as the lowest content of genetic material able to be detected in all 10 replicates. QIAstat-Dx and the WHO-recommended Charité RT-PCR assay for the E gene and RdRp gene were compared. QIAstat-Dx was tested using twofold dilutions of a second positive nasopharyngeal clinical sample (strain 2) around the previously estimated LoD until obtaining 10 replicates or a failed result. The in-house assay was tested for obtained LoD values using the same viral dilution conserved at +4°C, in the same 24 h.

^bThe estimated viral load (in copies per milliliter [cp/ml]) and replicate number are shown.