2 Tests to guide decisions about using antibiotics
2.1 Consider the following tests to help inform decision making about using antibiotics:
microbiological samples for routine culture and sensitivities (for example, sputum or tracheal aspirate sample, blood culture)
SARS‑CoV2 polymerase chain reaction assay (nasopharyngeal aspirate, nose and throat swabs, or a lower respiratory tract sample if obtainable); see Public Health England's guidance on COVID-19: which samples should be taken)
chest imaging (X‑ray, CT or ultrasound)
full blood count
legionella and pneumococcal antigen tests (urine sample).
There is insufficient evidence to recommend routine procalcitonin testing to guide decisions about antibiotics. Centres already using procalcitonin tests are encouraged to participate in research and data collection (see section 6).
Procalcitonin tests could be useful in identifying whether there is a bacterial infection. However, it is not clear whether they add benefit beyond what is suggested in recommendation 2.1 to guide decisions about antibiotics. The most appropriate threshold for procalcitonin is also uncertain.
2.3 Be aware that high C‑reactive protein levels do not necessarily indicate that the pneumonia is due to bacteria rather than COVID‑19.
Published data and clinical opinion suggest that many patients with COVID‑19 have raised C‑reactive protein levels, meaning that this does not necessarily indicate that there is a bacterial infection.