Podcast 557: COVID-19 Lab Trends

<p><strong>Contributor: Don Stader, MD</strong></p> <p><strong>Educational Pearls:</strong></p> <p> </p> <ul> <li><strong><span style="font-weight: 400;">COVID-19 is diagnosed with a nasopharyngeal swab (q-tip). This unfortunately can be painful, but if the swab doesn’t go deep into the nasal cavity the sample can be inadequate leading to false negatives (missed infections).</span></strong></li> </ul> <ul> <li><span style="font-weight: 400;">The sensitivity of the COVID-19 RT PCR test is low, ranging from 66-80% in various studies. Another study has shown 23% of patients who initially tested negative but had COVID-19 symptoms will test positive when re-tested. So test highly suspicious patients twice. </span></li> </ul> <p> </p> <ul> <li style="font-weight: 400;"><span style="font-weight: 400;">COVID has shown to have an effect on CBC. White blood cell counts are often normal (no leukocytosis), but there is often lymphopenia, or low lymphocytes, and thrombocytopenia. Interestingly, low platelets have appeared to have prognostic value in that lower platelets often indicate worse patient outcomes. </span></li> <li style="font-weight: 400;"><span style= "font-weight: 400;">Coagulation studies are showing very elevated D-Dimers which has sparked the debate as to whether COVID-19 causes a hypercoagulable state. The increased incidence  of MI/heart attacks and strokes in COVID patients supports this argument.  </span></li> <li style="font-weight: 400;"><span style="font-weight: 400;">While D-Dimers can help point towards a diagnosis of pulmonary embolism, in the setting of highly likely COVID-19 infections, getting a CTA looking for a PE is probably unnecessary unless there’s also suspicion for PE. </span></li> <li style="font-weight: 400;"><span style= "font-weight: 400;">C-reactive protein (CRP) and procalcitonin are two common inflammatory markers. A CRP can help indicate how sick a patient is and procalcitonin can help determine if the infection is bacterial or viral in nature. </span></li> <li style="font-weight: