Development of quantum dot-based fluorescence lateral flow immunoassay strip for rapid and quantitative detection of serum interleukin-6

BACKGROUND

Interleukin-6 (IL-6) is an inflammatory factor that increases rapidly in response to infectious diseases including sepsis. The aim of this study is to develop a quantum dot (QD)-based fluorescence lateral flow immunoassay (LFIA) strip that can rapidly and accurately detect IL-6 levels.

METHODS

QD-based LFIA strips were fabricated by conjugating CdSe/ZnS QDs to the IL-6 antibody. Performance verification and clinical sample analysis were carried out to evaluate the newly developed strip.

RESULTS

QD-based LFIA strips were successfully fabricated. The test strip's linear range was 10-4000 pg/ml, with a linear correlation coefficient of R²  ≥ .959. The sensitivity of the test strip was 1.995 pg/ml. The recovery rate was 95.72%-102.63%, indicating satisfying accuracy. The coefficient of variation (CV) of the intra-assay was 2.148%-3.903%, while the inter-assay was 2.412%-5.293%, verifying the strip's high precision. The cross-reaction rates with various interleukins (IL-1α, IL-1β, IL-2, IL-4, and IL-8) and interferon-γ (IFN-γ) were all <0.1%. When the strip was placed in a 50°C oven for 1, 2, 3, and 4 weeks, the test results were not significantly altered compared to storage at room temperature. Furthermore, 200 clinical serum samples were analyzed to compare the strip with the Beckman chemiluminescence immunoassay (CLIA) kit, which revealed a high correlation (n = 200, R²  = .9971) for the detection of IL-6.

CONCLUSIONS

The QD-based test strip can rapidly and quantitatively detect IL-6 levels, thus meeting the requirement of point-of-care test (POCT) and showing excellent clinical prospects.

[Clinical value of fluorescence lateral flow immunoassay in diagnosis of influenza A in children]

OBJECTIVE

To evaluate the clinical value of a new type of fluorescence lateral flow immunoassay in rapid detection of influenza A virus.

METHODS

A total of 378 samples of nasopharyngeal secretions were collected from 378 children with influenza-like symptoms to detect the influenza A virus by fluorescence lateral flow immunoassay, colloidal gold immunoassay, and RT-PCR between July 2015 and August 2015.

RESULTS

Of the 378 samples, 81 (21.4%) were positive for influenza A virus by RT-PCR. Compared with RT-PCR, the sensitivities of fluorescence lateral flow immunoassay and colloidal gold immunoassay were 90.1% (73/81) and 75.3% (61/81), respectively, and the specificities were 99.3% (295/297) and 98.3% (292/297), respectively. The average threshold cycle (Ct) value for the positive samples detected by the fluorescence lateral flow immunoassay (30.6) was higher than that for the positive samples detected by the colloidal gold immunoassay (28.7).

CONCLUSIONS

Compared with colloidal gold immunoassay, fluorescence lateral flow immunoassay has higher sensitivity, specificity, and concordance rate with RT-PCR, suggesting that it can be used for early screening and diagnosis of influenza A.