Why TPR is no longer the right metric to gauge COVID-19 spread

It is high time we ditch TPR, focus on ICU Occupancy Rate as a key metric

A BMC health worker collects swab sample of a passenger for COVID-19 test, at a station in Mumbai, Wednesday | PTI A BMC health worker collects swab sample of a passenger for COVID-19 test, at a station in Mumbai, Wednesday | PTI

TPR is now an all too familiar acronym in our lexicon. The young and the old alike closely follow the daily official government statements on the latest TPR.

TPR or Test Positivity Rate is a proportion of the total number of positive COVID-19  results among the total number of tests done in a day. It is often used by health authorities as a metric to gauge the extent of infections in a community.

Unfortunately, it is not a fool-proof metric. It is dependent on a number of other factors. For instance, if more people opt for antigen tests instead of RT-PCR tests, there is a chance for TPR to be lower as compared to a real estimate. It is also dependent on whether we test family members of patients with COVID-19 or not—this will increase the number of positive results. It is, however, not an uncommon practice to assume (even without testing) that the rest of the people at a COVID-positive person's home would have contracted the infection. A health system that aggressively tests household members of COVID-19 patients will have a higher TPR in comparison to one that does not. I believe this is one of the reasons Kerala’s TPR remains high when compared to the rest of the nation. Day-to-day variations in TPR can be accounted by several such factors.

TPR was a useful metric in the initial phase of the pandemic, especially in the mitigation stage. Must TPR be the be-all and end-all for COVID-19 surveillance during the current times? Let me propose a better metric. I suggest we closely monitor and emphasise ICU Occupancy Rate (IOR) as the key metric for COVID-19 surveillance henceforth.

To understand this metric, one must understand the real harms of COVID-19. We know by now that the vast majority of COVID-19 infections resolve on their own. Most patients need nothing more than good rest and a few paracetamol pills. However, a small proportion of patients develop severe conditions that require hospitalisation and intensive care. And, it is not easy to predict the disease course for most patients early-on. To some extent, that has changed. We know that the elderly and persons with comorbidities like diabetes are at a greater risk of severe disease. Hence, we focused the early phase of the vaccination campaign on immunising them.

Besides, we now have effective medicines that can prevent worsening of the disease, albeit the expense. We also know, to a large extent, what medicines work well and what do not. We have also mobilised and built capacity in healthcare systems vis-a-vis more oxygen production plants, ventilators, oxygen concentrators and ICU beds.

Another reason for such a proposal to dump TPR for IOR as the key metric is that we have given at least one dose of vaccine to a third of our population. We know that a dose of Covishield vaccine provides around 70 per cent protection against severe disease. As we improve the vaccination coverage, the chances of severe disease and healthcare resource utilisation reduce dramatically, as seen in Israel and the US.

Also, TPR does not assess the preparedness of the health system in any meaningful way. Instead, the IOR is a direct measure of that.

But, the major reason why I propose to dump TPR as the key metric is the harm it is causing the economy. Policymakers are using TPR to measure the extent of COVID-19 spread in a community, based on which they have been enforcing extended lockdowns and therefore hurting the economy.

SARS-CoV2 is a smart bug. It has shown remarkable skills in adapting to situations. We must be smarter than the bug to beat it. Let us dump TPR for the IOR as the key metric to assess COVID-19 surveillance and health system preparedness.

The author is an oncologist and hematologist

The opinions expressed in this article are those of the author's and do not purport to reflect the opinions or views of THE WEEK.