Diagnostic utility of CRP to neopterin ratio in patients with acute respiratory tract infections.

OBJECTIVES: In this study we aimed to investigate the roles of neopterin, C-reactive protein (CRP) and the CRP to neopterin (C/N) ratio to differentiate bacterial from viral aetiology in patients with suspected acute respiratory tract infections (ARTIs) presenting to the emergency department (ED). METHODS: Serum was taken from five hundred and sixty-one patients and used to measure neopterin and CRP levels. The primary outcome was bacterial or viral infection based on positive bacterial culture and positive viral serology. Patients were classified as either: group 1 with positive bacterial culture and mixed bacterial/viral growth; group 2 with virological aetiology, and group 3 with unknown microbiological aetiology. RESULTS: The median of the C/N ratio was 10 times higher in patients with bacterial aetiology than with viral aetiology (12.5 vs 1.2mg/nmol; P<0.0001), and 42 times higher than those in healthy subjects (12.5 vs 0.3mg/nmol; P<0.0001). The area under the receiver-operator characteristic curve for the C/N ratio was 0.840 (0.783-0.898; P<0.05). A cut-off value of "C/N ratio >3" for ruling in/out bacterial/viral infection yielded optimal sensitivity and specificity of 79.5% and 81.5% respectively. A sensitivity analysis performed on all patients (including unknown aetiology) with a cut-off value of "C/N ratio >3" yields a best-case scenario for ruling in/out bacterial/viral infection with sensitivity of 93.1% and specificity of 93.0%. CONCLUSION: This study shows that CRP and neopterin have a role in differentiating bacterial from viral causes of ARTI, and the C/N ratio yields optimal differentiation in the ED setting.

InfectCheck CRP barcode-style lateral flow assay for semi-quantitative detection of C-reactive protein in distinguishing between bacterial and viral infections.

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.

Value of serum procalcitonin, neopterin, and C-reactive protein in differentiating bacterial from viral etiologies in patients presenting with lower respiratory tract infections.

The values of procalcitonin (PCT), neopterin, and C-reactive protein (CRP) alone and in combination to differentiate bacterial from viral etiology in patients with lower respiratory tract infections (LRTIs) were evaluated. Sera obtained on the day of hospitalization for LRTI from 139 patients with confirmed bacterial etiology and 128 patients with viral etiology were examined. A further 146 sera from healthy Chinese subjects with no infection were included as controls. The area under the receiver operating characteristic (ROC) curve (area under curve [AUC]) for distinguishing bacterial from viral infections was 0.838 for CRP and 0.770 for PCT (P < 0.05). The AUC for distinguishing viral from bacterial infections was 0.832 for neopterin (P < 0.05). When the markers were used in combination, AUC of ROC (CRP/neopterin) was 0.857, whereas (CRP x PCT)/neopterin was 0.856. Combination of 2 or all 3 of the biomarkers may improve the discriminatory power in delineating bacterial versus viral etiology in LRTI.

Serum neopterin for early assessment of severity of severe acute respiratory syndrome.

Neopterin and C-reactive protein (CRP) concentrations were determined in serum samples from 129 severe acute respiratory syndrome (SARS) patients and 156 healthy blood donors. In the patients with confirmed SARS, an early neopterin elevation was detected already at the day of onset of symptoms and rose to a maximum level of 45.0 nmol/L 3 days after the onset. All SARS patients had elevated neopterin concentrations (>10 nmol/L) within 9 days after the onset. The mean neopterin concentrations were 34.2 nmol/L in acute sera of SARS patients, 5.1 nmol/L in convalescent sera, and 6.7 nmol/L in healthy controls. In contrast, the mean CRP concentrations in both acute and convalescent sera of SARS patients were in the normal range (<10 mg/L). Serum neopterin level in SARS patients was associated with fever period and thus the clinical progression of the disease, while there was no significant correlation between the CRP level and the fever period. Serum neopterin may allow early assessment of the severity of SARS. The decrease of neopterin level was found after steroid treatment, which indicates that blood samples should be collected before steroid treatment for the neopterin measurement.

One-step quantitative cortisol dipstick with proportional reading.

Rapid quantitative immuno-detection of haptens by the lateral flow assay without "typical" competitive inhibition results is studied. In the present study, we describe an immuno-threshold-based assay for the quantification of cortisol. It gives a signal which is directly proportional to the cortisol concentration in plasma samples with a performance time of only 5 min. This technique provides a practical calibration curve with detection limit of 3.5 ng/ml. The precision of the assay is 6% (intra-assay coefficient of variation, CV) and 10% (inter-assay CV). Cross-reactivity with related steroids is acceptably low: corticosterone (3.38%), cortisone (2.08%), deoxycorticosterone (2.00%), 17alpha-hydroxyprogesterone (0.39%), and progesterone (0.05%). Furthermore, the test strips show the advantages of long storage time and high stability that allow mass production and preparation of large batches. A one-step cortisol whole blood test derived from this plasma lateral flow assay has then been performed. It is a rapid chromatographic immunoassay designed for quantitative determination of cortisol in whole blood samples. It requires no sample pretreatment and gives result within 15 min. In principle, with this rapid and sensitive immunoassay, the immuno-test strips can be employed for detecting all low-molecular-weight haptens. It may also be a useful and convenient dipstick format for drug detection.