In the present study, we describe an InfectCheck barcode-style lateral flow assay for semi-quantitative detection of CRP in distinguishing between bacterial and viral infections. The severity of bacterial infection can be assessed by simply counting the number of red lines developed at the CRP test zone of the test device. If only one visible line appeared at the CRP test zone, it represents a low or mild inflammation with CRP levels <10 mg/L. Two and three visible lines mean moderate (>or=10-25 mg/L) and severe (>or=25-50 mg/L) inflammations respectively while four visible lines stand for a very severe inflammation (>or=50-100 mg/L). If the visible lines become faint and the intensity of the first line is weaker than that of the control line and may even disappear, this outcome corresponds to the stage of having super severe inflammation (>or=100 mg/L). A total of 500 patients admitted to hospital through the Accident and Emergency Unit at the Prince of Wales Hospital were examined. The InfectCheck CRP barcode-style rapid test gave a high sensitivity of 88.7% and a high negative predictive value of 93.8%. This result indicates that the rapid test is reliable to exclude non-infected patients. The calculated intra- and inter-assay coefficient of variation for the five CRP concentration ranges was both within 20.0%. It is a one-step whole blood rapid test without any sample pre-treatment and the result is available within 20 min. This user friendly diagnostic tool can allow self-testing by interested individuals without any expensive reading device.