Table 4 Summary of thermal degradation assessments of candidate standards HPV6, 11, 31, 33, 45, 52 and 58 tested by reference laboratories REF-1 and REF-2 using PBNA and antibody-binding methods

From: WHO International Standards for antibodies to HPV6 HPV11 HPV31 HPV33 HPV45 HPV52 and HPV58

 

Predicted loss per year at −20 °C

Candidate Standard

Time at elevated temperatures (years)

REF-1 (PBNA)

REF-2 (PBNA)

REF-1 (Ab-Binding)

REF-2 (Ab-Binding)

HPV6

1.14

*

< 0.001%

5.23%**

0.02%

HPV11

0.25

*

*

22.3%**

Not tested

HPV31

0.46

*

*

*

0.00%

HPV33

1.64

*

*

0.14%

0.01%

HPV45

0.46

*

***

*

0.02%

HPV52

1.64

*

0.001%

0.22%

0.00%

HPV58

1.14

*

*

1.90%**

0.02%

  1. *No or poor model fit, no prediction of loss made. **The lack of observable real-time degradation over relatively short time spans can result in predictions of unrealistically high degradation rates using Ab-binding assays. ***Estimates not obtained for HPV45 assay due to technical issues with the assay. See Supplementary Tables 14−18 for real-time stability results.
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