• health services research
• epidemiology
• quality indicators, health care
• patient care team

Cardenas-de la Garza et al 1 ask a reasonable question that nowadays likely resonates in many rheumatological practices: “Should we screen our patients who start biologics for SARS-CoV-2?” As so often in medicine, the question is easily asked but is more difficult to answer.

First of all, screening implies the availability of a diagnostic test to be applied in a patient that does not have symptoms (yet). For SARS-CoV-2, we have two types of tests available: the PCR test, known as the ‘swab-test’, which proves the presence of the virus, and the antibody test, which proves the presence of antibodies against the virus.

The PCR test has as narrow window and is likely only positive for a while, when the patient is sick already or will get complaints soon. Asymptomatic carriership for SARS-CoV-2 is an arguable concept, if existent anyway. In addition, like every diagnostic test, the PCR test is not free of sensitivity and specificity problems. False negativity is a well-known issue, although manageable in a context of a patient with a typical clinical picture during an epidemic phase. The positive predictive value of the PCR test is likely very high during an epidemic phase, when many patients present with COVID-19 symptoms, but unknown when the epidemic is gone and the incidence is low.

Widely available and reliable antibody tests are lacking for the moment, and more importantly, we know far too little about the performance of these tests and about the consequences of a positive test for the patient. Does a positive test mean that you cannot start a biologic? Does it harm such a patient? Does a positive test indicate temporal or persistent immunity for SARS-CoV-2? What about cross-reaction with other coronaviruses?

We are of the opinion that we should learn a lot more before we can start thinking about such a delicate matter as screening. Screening may seem simple and straightforward, but it is awfully complicated and will lead both to false reassurance and unnecessary anxiety. For now, we strongly discourage screening for SARS-CoV-2 to be applied in patients with rheumatic and musculoskeletal diseases, whether or not they will start a biologic.