COVID-19 Testing

Labs submit testing data to the State in two ways: at the patient-level, and in aggregate.

Patient-level testing data (positives and negatives) is submitted either electronically through NC COVID or manually via secure fax or electronic communications. Approximately 80% of total patient-level tests are now submitted electronically through NC COVID. The other 20% that are manually submitted must then be hand-entered into NC COVID.

Aggregate testing data is provided by labs that don’t have electronic laboratory reporting. These labs submit the daily number of tests performed to NCDHHS using the electronic COVID-19 Aggregate Test Reporting (eCATR) survey tool.

Test totals are combined from these two sources of testing data to obtain the daily and cumulative report of total tests performed. NCDHHS has been working to improve data reporting processes to minimize redundancy with all labs to move to reporting exclusively through NC COVID to improve data integrity with test totals from NC COVID to obtain the total number of tests conducted.

Tests can be reported in batches (e.g., a lab reports three days of testing data at once) and tests are not always reported on the day they occurred. When a new lab begins reporting, it may report a backlog of tests from the past days or weeks. When tests are reported in batches or a new laboratory begins reporting, those tests are assigned back to the correct date. Therefore, previous days of testing are updated as more tests are reported. The number of tests completed by day is a dynamic number and is dependent on reporting labs.

Total tests represent the number of tests reported to NCDHHS for that day. This tells us how much daily testing is increasing throughout the state. This includes both total tests that report daily through electronic laboratory reporting, and those that are submitted manually. Because tests can be reported in batches, dates may be backfilled, and data might fluctuate. Tests have been broken out to show molecular (PCR) vs. antigen tests completed starting with data on Sept. 22, 2020 on the “Total Tests Reported” chart. For dates prior to Sept. 22, 2020, test totals cannot be broken out according to test type due to data limitations in the process previously used for laboratory reporting of test totals. However, it is likely that antigen tests were included in aggregate totals submitted by laboratories in daily reports in the past.  

Percent positive represents the number of positive molecular (PCR) tests as a percentage of all molecular (PCR) tests reported electronically directly into NC COVID. We know that as we test more, the number of infections detected may go up. This metric gives us a sense of how many positive tests we are seeing in comparison to how much testing is being done. All data are preliminary and may change. 

To calculate positive tests as a percent of total tests NCDHHS only uses molecular (PCR) test results from laboratories that report both positives and negatives through electronic laboratory reporting in NC COVID. This ensures that the positive and negative tests were from the same day to calculate an accurate daily percent positive. This is because test totals that are not reported electronically can occur in batches, and it cannot be confirmed that the positives and negatives occurred on the same day. Antigen tests are excluded from percent positivity calculations at this time, but NCDHHS will be evaluating including them in calculations in the future.

Average Percent Positive by County

North Carolina uses labs reported electronically to provide county level testing data. Antigen tests are excluded from percent positivity calculations to align with current CDC definitions used to calculate percent positivity.

A limitation of this data is that we know that not all tests are reported electronically, and some counties may be more likely to use a lab that does not report electronically. County data serves as a starting place to help counties gauge their testing volumes.

Percent positive shows the trends in positive tests as a percent of total tests for tests that were reported electronically. Counties may not have any labs reported electronically on a given day. These will show up as no tests, and 0% positive for that day.

The percent positive displayed in the county map is the average percent positive during the last two weeks. If a county has only one week with less than an average of 50 daily tests, then that week will not be shown and not included in the average percent positive. If a county has both weeks with fewer than an average of 50 daily tests, then the graph will not be shown. Counties with fewer than an average of 50 daily tests for the two weeks are not shown because there are not enough electronically reported tests in that county to provide a reliable percent positive calculation. The percent positive may fluctuate substantially as there are a smaller number of tests than the state percent positive. All data are preliminary and subject to change.

Testing Turnaround Time

Testing turnaround time measures the time between when a person is tested, and when the result feeds into public health for tests that are electronically reported. Please note that the testing turnaround time doesn’t necessarily include the time between when a person is tested and notified of their results.

There are multiple stages that make up the time it takes from when a person is tested to the time the person receives their results – the testing turnaround time. The first stage is the time between when a specimen is collected to when it is received by a laboratory. Several factors can impact this timing, including how and when the specimen is transported to a laboratory. The second stage is the time between when the specimen is received and when the laboratory has a result. This first and second stage is shown in the dark purple in the graph below. The third stage is the time between when the laboratory determines a result and the laboratory electronically reported to NCDHHS. This third stage is shown in the light purple. The fourth stage, which is not represented in the graph below, is the time between when a laboratory reports a result and the patient is notified of their results. This fourth stage happens between the health care provider and patient and is not reported to NCDHHS. The yellow line shows the 7-day rolling average of the dark purple, when a specimen is collected to when the laboratory has a result.

Individual laboratories may have shorter or longer turnaround times and, therefore people's individual experience will vary. Antigen tests are excluded from testing turnaround calculations because antigen tests are designed to be rapid and are typically resulted within an hour or less. Including these tests in testing turnaround time calculations would potentially artificially decrease testing turnaround times for molecular (PCR) test results, which are the most widely used tests today.

Laboratory results received electronically for previous dates may cause slight variation in day-to-day reporting.