RELIABILITY AND FEASIBILITY OF A NEAR PATIENT TEST FOR C-REACTIVE PROTEIN IN PRIMARY-CARE

Background. The applications of new diagnostic technologies such as ne ar patient tests are relevant to the further development and potential of primary care. Through their use, doctors in the community may incr ease the accuracy of their diagnoses and improve their ability to moni tor disease. A reliable indicator of disease activity in various clini cal conditions is C-reactive protein (CRP) and a near patient test for this is now available, although there is little information on its us e outside hospitals. Aim. A study was set up to evaluate the feasibili ty of using a novel near patient test for CRP in primary care to valid ate the results against the laboratory 'gold standard' for CRP (Beekma n Array) and to compare results with the usual inflammation test used in general practice. Method. Prospective recording of CRP as a near pa tient test on an 'intention to investigate' basis, with validation of results against the Beekman Array system for CRP and hospital laborato ry erythrocyte sedimentation rate results, in six general medical prac tices in Birmingham. Main outcome measures were change in local labora tory usage, characteristics of patients chosen for testing, use of qua lity control, and comparison of readings with results from the same sa mple sent to an independent laboratory. Results. Tests of CRP levels w ere rarely requested before the study was undertaken. During the 3-mon th study period, 181 near patient tests were carried out, 146 (81%) to establish a diagnosis and the remainder for disease monitoring. Out o f the tests, 67% were performed by general practitioners, mostly durin g the consultation itself. Using a cut-off level of 10 mg l(-1), the n ear patient test and the Beekman Array gave results which agreed in 84 % of cases. The sensitivity and specificity of the near patient test r esults were 97 and 79%, respectively. The predictive value of a positi ve result was 59% and that of a negative result was 99%. Cohen's Kappa was 62% and the overall mean bias for results in the range of the tes t was 6.11 mg l(-1) (SE = 3.07 mg l(-1)). Each test took 6 min on aver age to perform, including all preparations, blood letting, performing the test and averaging the time for quality control estimations. The c ost per test averaged pound 1.72, rising to pound 4.17 including labou r, capital costs, quality controls and consumables (general practition er performing the assay at average frequency found in this study). Con clusions. Measurement of CRP is rarely used in primary care and awaren ess of its value could be raised. This near patient test proved feasib le for use by general practitioners and practice nurses. Its reliabili ty compared with a laboratory result was satisfactory overall, and exc ellent with adequate operator technique.