Enhancing the accuracy of seroprevalence studies: Reassessing pertussis infection rates in eastern China during the COVID-19 pandemic

KEYWORDS:

• Vaccine
• factors
• pertussis

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The seroepidemiology of immunoglobulin G antibodies against pertussis toxin and filamentous hemagglutinin in the east of China during the COVID-19 pandemic

Dear editor, we would like to share ideas on “The seroepidemiology of immunoglobulin G antibodies against pertussis toxin and filamentous hemagglutinin in the east of China during the COVID-19 pandemic.”¹ The study, conducted in eastern China, attempted to determine the incidence of pertussis in a healthy population by quantifying IgG antibodies against pertussis toxin (anti-PT) and filamentous hemagglutinin (anti-FHA) using ELISA. The study found a significant incidence of pertussis in 2022, with the greatest seropositivity rate in the 1–2-year-old group. However, the projected pertussis infection rate based on seroprevalence was roughly 25,625 times greater than the reported notification rate among people aged 15 and older.

One potential issue with the second research is the accuracy and reliability of the immunological technique employed to detect IgG antibodies.² According to the earlier publication, 99.6% sensitivity and 99.2% specificity of the assay were reported. The process may not have been adequately standardized or calibrated, resulting in discrepancies in the results. Furthermore, the assay’s sensitivity and specificity may not have been fully evaluated, which could have an impact on the findings’ validity.

Therefore, it would be important to re-analyze the data from the study after adjusting or correcting any issues related to assay sensitivity and specificity. By ensuring that the assay used is calibrated correctly and accurately reflects the levels of IgG antibodies, the results of the study can be more reliable and robust. This re-analysis would provide a more accurate estimate of pertussis incidence within the population and offer valuable insights for improving immunization strategies and public health policies.

After accounting for the issue of assay sensitivity and specificity, the estimated pertussis infection rate based on seroprevalence may need to be revised. Because the study’s sensitivity estimates were likely overestimated due to the absence of pertussis patients with IgG responses, the recalculated pertussis infection rate based on seroprevalence may be lower than the previously reported estimate.

To recalculate the predicted rate of pertussis infection based on seroprevalence after accounting for test sensitivity and specificity, we can utilize the genuine sensitivity of 99.6% and specificity of 99.2%.

To recalculate the estimated rate of pertussis infection based on seroprevalence after adjusting for assay sensitivity and specificity, we can use the true sensitivity of 99.6% and specificity of 99.2%. Here are steps for modeling.

1. Calculate the true positive rate (TP), false positive rate (FP), true negative rate (TN), and false negative rate (FN), using the sensitivity and specificity values:

2. TP = 99.6%

3. FP = 100% - Specificity = 100% − 99.2% = 0.8%

4. TN = Specificity = 99.2%

5. FN = 100% - Sensitivity = 100% − 99.6% = 0.4%

1. Adjust the seroprevalence data based on the TP, FP, TN, and FN rates:

2. Estimated rate of pertussis infection based on seroprevalence × (TP/(TP + FN)) = Adjusted estimated rate of pertussis infection.

1. Use the adjusted values to recalculate the estimated rate of pertussis infection based on seroprevalence.

By incorporating the true sensitivity and specificity values into the calculation, a more accurate estimate of the rate of pertussis infection based on seroprevalence can be obtained.

Here, estimated rate of pertussis infection based on seroprevalence × (99.6%/(99.6% + 0.4%)) = Adjusted estimated rate of pertussis infection.

Adjusted estimated rate of pertussis infection = Estimated rate of pertussis infection based on seroprevalence × (99.6%/100%) = Estimated rate of pertussis infection based on seroprevalence.

Therefore, the estimated rate of pertussis infection based on seroprevalence remains the same after adjusting for assay sensitivity and specificity, as the sensitivity and specificity values provided are both very high and do not significantly impact the calculation.

Authors’ contribution

HP 50% ideas, writing, analyzing, approval.

VW 50% ideas, supervision, approval.

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No potential conflict of interest was reported by the author(s).

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Funding

The author(s) reported there is no funding associated with the work featured in this article.