This affects how the meaning of percent positivity results are interpreted. Sometimes the criteria for testing - routine screening versus diagnostic testing of symptomatic people - is not known. Differences in inclusion of screening test results.CDC recommends reporting positive results for SARS-CoV-2 antigen tests as a separate metric. Differences in the inclusion or exclusion of antigen test results, which are inconsistently reported.Other differences can include the date used - specimen collection date, test date, result date - to assign tests to specific timeframes. Differences in the timeframe for including data (a seven-day versus a 14-day rolling average, for example).CDC, however, is unable to perform this function and can only calculate tests/tests. This allows them to identify and de-duplicate people with multiple positive tests. State, local, and territorial health departments have access to personal identifiers in their datasets. Differences in the numerators or denominators used - such as tests/tests, people/tests, people/people.Methods used by jurisdictions to calculate percent positivity can differ, including the following: Varying Methods to Calculate Percent Positivity An example would include prioritizing reporting of positive test results over negative results. There are reporting processes or delays that skew the results.Only those at greatest risk of infection within a community are being tested.There are widespread infections in the community tested.A high NAAT percent positivity occurs when many of the test results among those being tested and reported in a community are positive. Percent positivity can vary depending on the volume of testing and the population tested. While calculation methods among jurisdictions can differ, percent positivity has provided insights into transmission of SARS-CoV-2 within a geographic area (e.g., national, regional, state, county). In general, laboratory test percent positivity as reported by CDC has represented the percentage of all SARS-CoV-2 NAATs conducted that are positive. When calculating percent positivity, CDC excludes antigen and antibody tests from both the numerator and denominator. Multiply the result by 100 to obtain the percentage.Īnother way to look at this formula is positive tests/total tests x 100.Divide the numerator by the denominator.Obtain the denominator - the total number of SARS-CoV-2 NAAT test results, both positive and negative.Obtain the numerator - the number of positive SARS-CoV-2 Nucleic Acid Amplification Test (NAAT) results.Using Percent Positivity Calculation for Public Health SurveillanceĬDC has a formula for calculating percent positivity of laboratory test results. Data can be downloaded for analysis from external icon. CDC makes SARS-CoV-2 test result data available to the public on CDC’s COVID Data Tracker website. CDC and HHS process and analyze the data, and results are made available in HHS Protect for use by the federal response. ) All information is de-identified to protect individual privacy.
#Figuring percentages pdf
(See CARES Act Section 18115 pdf icon external icon. Data are then transmitted from states to CDC as required by the Coronavirus Aid, Relief, and Economic Security (CARES) Act. SARS-CoV-2 test result data are reported to state, local, and territorial health departments by public health laboratories, clinical laboratories, some large chain drug stores, and other testing entities as required by state and local laws.
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