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Contribution of second stool specimen to increased sensitivity of poliovirus detection in India, 1998-2000
K A Kohler1, J M Deshpande, H E Gary
1Global Immunization Division, National Immunization Program, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA.
Abstract:
Acute flaccid paralysis (AFP) surveillance data from India were analysed to examine sensitivity of poliovirus isolation from stool specimens and the added sensitivity obtained from collection of a second stool specimen. Analysis was restricted to Indian AFP cases, 1998-2000, with two adequate stool specimens. The proportion of cases confirmed with wild poliovirus isolation by the second specimen only was calculated, regardless of specimen quality. Overall specimen sensitivity (1998-2000) was 81% using the first specimen, 78% using the second, and 96% using both. Sensitivity increased from 1998 to 2000, with slightly higher sensitivity each year for the first specimen. The second specimen increased sensitivity by 15% overall and contributed more when the first specimen was collected late or was in poor condition. As wild poliovirus disappears, increased sensitivity provided by a second stool specimen may reduce the risk of missing circulating virus.
Insights
Collecting a second stool specimen significantly enhances acute flaccid paralysis (AFP) surveillance sensitivity for poliovirus detection. This strategy is crucial for reducing the risk of missing circulating wild poliovirus, especially as it becomes rarer.
Area of Science:
- Virology
- Epidemiology
- Public Health
Background:
- Acute flaccid paralysis (AFP) surveillance is critical for detecting poliovirus transmission.
- Accurate and sensitive detection of wild poliovirus is essential for eradication efforts.
Purpose of the Study:
- To evaluate the sensitivity of poliovirus isolation from stool specimens in India.
- To determine the added sensitivity gained by collecting a second stool specimen for AFP surveillance.
Main Methods:
- Analysis of Indian AFP surveillance data from 1998-2000.
- Inclusion of cases with two adequate stool specimens.
- Calculation of poliovirus isolation rates for first, second, and both specimens.
Main Results:
- Overall specimen sensitivity was 81% for the first, 78% for the second, and 96% for both specimens.
- The second stool specimen increased overall sensitivity by 15%.
- Increased sensitivity from the second specimen was more pronounced with late or poor-quality first specimens.
Conclusions:
- A second stool specimen significantly enhances poliovirus detection sensitivity in AFP surveillance.
- This improved sensitivity is vital for minimizing the risk of missing poliovirus cases, particularly in low-prevalence settings.
- The findings support the continued use of dual specimen collection in poliovirus surveillance programs.