TPR is a reflection of disease transmission but it is dependent on a number of factors
The government’s over emphasis on test positivity rate (TPR) as the epidemiological indicator of COVID-19 transmission without any scientific understanding of the concept and pegging lockdown relaxations in local bodies to TPR has led to a situation wherein grama panchayats are now competing with each other to reduce TPR by hook or crook.
TPR is the proportion of people who turn positive amongst the total number of tests done in a geographical region. While it is indeed a reflection of disease transmission in a region, the robustness of TPR as an indicator is dependent on a number of factors, especially the volume of tests done and who is being tested.
When the government lifted the 40-day lockdown, it was stipulated that the weekly average TPR in a local body will decide the levels of lockdown relaxations.
Since the past one week, local bodies are given a daily testing target based on their TPR. Testing numbers are increased several fold, depending on how high the TPR is.
“Local bodies are struggling to meet this target because people are resisting testing due to the fear of stigma, loss of livelihood, and freedom. For the local bodies, reduction of TPR has become an issue of their political image and local popularity because a high TPR and lockdown is projected as a measure of their inefficiency. The focus of all local bodies have thus shifted from the implementation of proper containment measures to the mere reduction of TPR,” a health inspector in a grama panchayat in Thiruvananthapuram district said.
Many district medical officers (DMOs) are also unhappy about the state of affairs. “Reducing disease containment efforts to just TPR reduction is totally unscientific and unproductive. Many such decisions are being imposed by higher ups without even consulting us or reckoning in our vast years of experience in the field,” a DMO, who refused to be named, said.
He pointed out that most local bodies were quite familiar with the ways and means in which TPR could be manipulated and brought down. Increasing the denominator by testing a large population and testing within a relatively low-risk population can artificially bring about a reduction in TPR.
“If we follow up a positive case and test all primary contacts within five days of exposure, we can capture most of the positive cases in the community. But now that TPR reduction is a mere exercise to get out of lockdown, the local bodies know that the less positive persons you find, the better. Because of the insistence on a fixed testing target and TPR-based lockdown release, all local bodies are busy holding testing camps where asymptomatic persons are herded in, so that TPR number can be reduced overnight,” one of the DMOs said.
People with symptoms were being told to stay home quietly, rather than test, he added.
“In a community with established active transmission, there is no point in sentinel surveillance testing or testing of asymptomatic individuals. What we need at this time is targetted testing of high risk individuals, especially primary contacts. This may push up the TPR but it will give us the right picture of the epidemic and help in focussed containment,” a public health expert said.
Directing all attention towards TPR reduction would result in the State actually missing pockets where disease transmission was live, he cautioned.