A patient walks into a GP surgery with a cough and a temperature. Clinically, it is often impossible to tell in the consultation room whether the cause is viral or bacterial, and that uncertainty is exactly what drives a large share of unnecessary antibiotic prescribing. CRP point-of-care testing gives the clinician a number, in minutes, that helps close that gap without sending a sample to a laboratory and waiting days for the answer.
C-reactive protein is a marker the liver produces in response to inflammation, and it rises more sharply and predictably in bacterial infection than in most viral illness. A point-of-care CRP device takes a small fingerstick blood sample and returns a numerical result at the desk, turning a subjective "does this look bacterial" judgement into a threshold-based decision that can be documented and audited.
The three CRP bands NICE guidance uses
For adults with a lower respiratory tract infection where diagnosis is uncertain after clinical assessment, NICE guidance sets out three CRP bands that map to different prescribing actions:
| CRP result | What it suggests | Recommended action |
|---|---|---|
| Below 20 mg/litre | Bacterial infection unlikely | Antibiotics not routinely offered |
| 20 to 100 mg/litre | Uncertain; low probability of serious bacterial infection in most patients | Consider a back-up (delayed) prescription rather than an immediate one |
| Above 100 mg/litre | Bacterial infection and risk of pneumonia more likely | Offer antibiotic therapy without delay |
These bands are a decision aid, not a replacement for clinical judgement. A patient with a low CRP but signs of clinical deterioration, or relevant comorbidities such as a COPD exacerbation with purulent sputum, may still warrant treatment that the number alone would not suggest. The point of the test is to add a reproducible data point to a decision that would otherwise rest entirely on how the consultation felt.
What the evidence shows about prescribing rates
The case for CRP point-of-care testing in general practice rests less on the biology and more on what happens to prescribing behaviour once it is introduced. Trials and meta-analyses of CRP testing for respiratory tract infections in primary care have reported reductions in antibiotic prescribing at the index consultation, with some studies showing a meaningfully lower rate of prescribing compared with usual care, and reviews finding no evidence that the reduction compromises patient safety or satisfaction. The effect appears to be larger still when the test is paired with brief communication-skills training for the clinician, since much of the pressure to prescribe comes from managing patient expectations as much as from clinical uncertainty. Similar reductions have been reported specifically for COPD exacerbations, where CRP testing has been shown to lower the proportion of patients started on antibiotics without a corresponding rise in re-consultations or treatment failure.
A second, less obvious effect shows up in delayed or "back-up" prescriptions. When a back-up prescription is issued alongside a CRP result in the intermediate band, patients appear less likely to actually collect and use it than when a back-up prescription is issued on clinical grounds alone. The number seems to function partly as a behavioural anchor: a low or middling reading reassures both clinician and patient that watchful waiting is a reasonable choice, not a gap in care.
What deploying this actually requires at the surgery
Adopting CRP point-of-care testing is not simply a matter of buying a device. A workable service needs a defined internal quality control routine so results can be trusted between formal external quality assessment cycles, a nominated point-of-care testing coordinator responsible for calibration, consumable stock and staff competency records, and a documented standard operating procedure that ties each CRP band to an agreed clinical action so the test result actually changes what happens next rather than becoming an extra number in the notes. Staff running the test, whether clinical or non-clinical, need training that is recorded and periodically refreshed, and the practice needs a clear line of accountability for who signs off the quality assurance programme. None of this is exotic by NHS standards, but it is additional infrastructure layered onto a consultation that used to end with a prescription pad and nothing else.
Where this fits within community diagnostics more broadly
CRP testing sits alongside glucose meters, INR monitors and rapid strep tests as part of the near-patient testing capability that community and primary care settings are increasingly expected to hold in-house rather than referring out. The appeal in each case is the same: a result inside the consultation changes the decision made inside the consultation, instead of arriving after the patient has already left with, or without, a prescription. For antimicrobial stewardship specifically, that immediacy is the whole point. A CRP result that arrives three days later, once the sample has gone to a laboratory, cannot influence a decision that had to be made on the day.
The broader argument for CRP point-of-care testing in London’s GP surgeries is not that it replaces clinical judgement. It is that it gives that judgement a number to lean on, in a system under sustained pressure to prescribe fewer antibiotics without under-treating the patients who genuinely need them.