Since autumn 2020, all samples submitted to us for rtPCR SRRP testing are examined parallel to the Tetracore kit (EZ-PRRSV MPX) and the Biovet “in house” test. We recently compiled the results of tests conducted at the end of 2020 on 1514 various samples (serums, oral fluids, processing fluids, lungs). The results obtained at the beginning of 2021 have not been analyzed due to lack of time, but they seem to confirm the 2020 results.
The 1514 samples originate from 824 cases and about 385 farms. Unfortunately, we cannot be more precise regarding the number of farms because the same farm can be designated on the requests by different names. Two hundred and fifty-four (254) samples tested positive using one and/or the other test (16.8% positive samples).
Two hundred and thirty-six (236) samples tested positive with both tests and the 18 discordant results were for samples with very low viral loads (Ct 34). Using the Tetracore kit or the Biovet test as a standard gold test, the two tests demonstrate an equivalent relative sensitivity and specificity (95.16% and 99.53%) respectively, and an almost perfect agreement (kappa:0.957).
|Sensitivity||95,16% (CI : 91,73 – 97,21%)|
|Specificity||99,53% (CI : 98,97% – 99,78%)|
|Kappa coefficient||0,957 (almost perfect Correlation)|
In more than half of the cases for which discordant results were obtained, at least one additional sample was positive in both tests. In fact, no strain appears to have been missed by either test. In addition, for all concordant results, the Cts obtained with the Biovet test were, on average, slightly lower than those obtained with the Tetracore test (Figure 1).
In conclusion, considering the results obtained on more than 1500 samples, we can say that both tests perform very similarly. In order to reduce the risk of missing some strains, however, we have decided to continue systematically testing all samples submitted to us using both tests. This will be done at NO additional charge.
Please feel free to contact us for further information.
Christian Savard, Director, Molecular Biology R&D
Olivier Ariel, Head of the Molecular Biology Laboratory
André Broes, Technical Support Manager