In several instances, the basic information the two organizations use to run their calculations are slightly different, leading to different final numbers. For example, Kansas Department of Health and Environment (KDHE) reports new positive cases by the date the lab specimen is tested (or run), but JCDHE reports this data based on the date the specimen was collected. JCDHE does it this way to ensure that the lab result aligns as closely as possible with the onset date of illness. This nuance matters at the local level because JCDHE is conducting case investigations with the newly diagnosed people, but it can lead to differing data.
Ultimately, there are differences in the inputs state and local health departments factor into their data calculations. These departments perform different functions and have different questions they need the data to answer. An example of this is which cases KDHE and JCDHE count in their total case counts. KDHE includes a set of probable cases, which include those meeting clinical criteria AND epidemiological evidence, or cases that have presumptive lab evidence and EITHER clinical or epidemiological evidence.
These cases include those identified by antigen tests, which are usually performed as a point of care test and are faster but not as sensitive to identifying the presence of the virus. KDHE also includes antibody tests (also called serology tests), which is a blood test conducted after a recovery from COVID-19 to identify antibodies to COVID-19. Finally, KDHE’s case counts include close contacts to a lab-confirmed positive case who become symptomatic within a 14-day exposure window, regardless of a positive lab result. Counting probable cases is a common practice among infectious disease experts, especially those looking at large populations. The state health department must understand what is going on with community transmission while also accounting for variances across geography, testing capabilities, health department investigative capacity, quick access to labs, and positive cases who deny testing. Counting probable cases makes some assumptions based on the preponderance of evidence. Probable cases are not counted as positive until they are lab-confirmed, which is why KDHE says their “case counts are preliminary and subject to verification.”
JCDHE’s responsibility at a local level is different. Our data can be more exacting because we can hold steady certain realities about Johnson County, such as testing capacity, health department investigative ability, and lab access. Local health officers are empowered to issue public health orders, compelling residents to take specific actions such as staying home, closing businesses, etc. It is vital that officials have the most accurate case counts. Therefore, JCDHE’s final case counts only include PCR tests, which are more sensitive molecular tests.