C-reactive protein: Clinical applications in monitoring disease activity

C-reactive protein and neutrophil count laboratory test requests from primary care: what is the demand and would substitution by point-of-care technology be viable?

AIMS : C-reactive protein (CRP) and neutrophil count (NC) are important diagnostic indicators of inflammation. Point-of-care (POC) technologies for these markers are available but rarely used in community settings in the UK. To inform the potential for POC tests, it is necessary to understand the demand for testing. We aimed to describe the frequency of CRP and NC test requests from primary care to central laboratory services, describe variability between practices and assess the relationship between the tests.

METHODS

We described the number of patients with either or both laboratory tests, and the volume of testing per individual and per practice, in a retrospective cohort of all adults in general practices in Oxfordshire, 2014-2016.

RESULTS

372 017 CRP and 776 581 NC tests in 160 883 and 275 093 patients, respectively, were requested from 69 practices. CRP was tested mainly in combination with NC, while the latter was more often tested alone. The median (IQR) of CRP and NC tests/person tested was 1 (1-2) and 2 (1-3), respectively. The median (IQR) tests/practice/week was 36 (22-52) and 72 (50-108), and per 1000 persons registered/practice/week was 4 (3-5) and 8 (7-9), respectively. The median (IQR) CRP and NC concentrations were 2.7 (0.9-7.9) mg/dL and 4.1 (3.1-5.5)×10⁹/L, respectively.

CONCLUSIONS

The high demand for CRP and NC testing in the community, and the range of results falling within the reportable range for current POC technologies highlight the opportunity for laboratory testing to be supplemented by POC testing in general practice.

Recombinant antibody fragments allow repeated measurements of C-reactive protein with a quartz crystal microbalance immunosensor

C-reactive protein (CRP) is a serum marker highly upregulated in inflammation after bacterial infection. Robust, reliable and quick quantification of CRP would be a substitute for erythrocyte sedimentation rate (ESR) with superior diagnostic value. Quartz crystal microbalance (QCM) based sensors coated with specific antibodies and integrated into lab-on-chip systems are in development for rapid point of care quantification. In this study, we isolated three CRP specific single chain (sc)Fv antibody fragments using phage display from an antibody gene library. Their affinities ranged from 2.7 × 10(-8) to 1.0 × 10(-8) M when measured by surface plasmon resonance. ScFv antibody fragment LA13-IIE3 showed best affinity, high long-term stability and remarkable resistance to denaturation. This scFv antibody fragment was coupled to a QCM sensor. CRP quantification in up to 15 samples sequentially measured on the same sensor with intermitting regeneration by buffer was demonstrated.

The effects of pretransplant conditioning, graft-versus-host disease and sepsis on the CRP levels in bone marrow transplantation

To evaluate the diagnostic utility of C-reactive protein (CRP) for the detection of sepsis in bone marrow transplantation, CRP levels were analyzed after pretransplant conditioning and variably combined in septic, focal or viral infections with graft-versus-host disease (GvHD) in 64 bone marrow recipients. The CRP levels after pretransplant conditioning were low. The peak levels of CRP were influenced independently by the type of infection (p = 0.016; septic and viral infections were significantly different) and GvHD (p = 0.003). The area under the receiver-operator characteristic (ROC) curve for peak CRP in sepsis was 0.653 and 0.618 with and without GvHD, respectively. It was concluded that GvHD and the type of infection were independent determinants of the CRP responses. GvHD did not affect the extent of the CRP response. Therefore, although not highly specific for sepsis, CRP remains a useful detector of sepsis in bone marrow transplantation.

C-reactive protein serum levels in patients with ocular disease

Hepatocyte derived C-reactive protein (CRP) is a sensitive indicator for inflammatory or infectious processes in a variety of tissues. As several other plasma proteins it is regarded as part of the acute phase response to a variety of tissue damage. CRP is commonly used in general medicine as a tool for the follow-up of especially bacterial infections. However, it has not been widely used in ophthalmology. In the present study CRP values in serum samples from 51 patients with various acute ocular diseases were determined semiquantitatively. High CRP levels were found most frequently in patients with either preseptal cellulitis (83.3%) or endophthalmitis (25.8%) whereas in the serum of patients with keratitis and uveitis, CRP exceeded 20 mg/l in only 18.7% of the cases. In a control group of 10 patients with retinal detachment the mean CRP level was 2.3 mg/l (SD +/- 0.98 mg/ml). The clinical significance and the prognostic value of CRP determinations during ocular diseases are discussed.