Lateral-Flow Immunoassays

Lateral-flow immunoassays (LFTAs), also known as immunochromatographic test strips or dipsticks, are a form of rapid and portable immunoassay in which the test sample extract flows along a solid substrate via capillary action. The dipstick system is simple operationally, whereas the technology behind it is advanced and subtle. 

The liquid sample re-mobilizes the dried conjugate component, and the analyte (if present) in the sample interacts with the conjugate as both migrate into the next section of the strip, termed the reaction matrix. The reaction matrix is a porous nitrocellulose membrane onto which the other specific biological component has been immobilized as bands in specific areas of the membrane. These bands (termed test and control lines) serve to capture the analyte and/or the conjugate as they migrate past 

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Bogdanovic, J., M. Koets, I. Sander, et al. 2006. Rapid detection of fungal [alpha]-amylase in the work environment with a lateral flow immunoassay. J. Allergy Clin. Immunol. 118 1157-1163. 

Confirmatory laboratory testing has been limited to viral cultures with subsequent immunoassay testing, which has limited its use, making reliance on history and clinical signs for diagnosis. A new in-office test for the adenovirus has been marketed. The RPS Adeno Detector is a 10-minute, in-office, lateral flow immunoassay that detects the presence of adenovirus in suspected... 

Figure 12-S Schematic diagram of a lateral flow immunoassay for troponin T. fCourtesy Roche D/ognosticSj Mannheim, Germany.)...

The underlying principle of one-step, sofid-phase immunochromatography (also known as lateral flow immunoassay) is the inhibition of antigen-antibody capture on a porous membrane by a drug present in the specimen. Different applications of this measurement concept have been commercialized. 

Oku, Y., Kamiya, K., Kamiya, H., Shibahara, Y., Ii, T., and Uesaka, Y. (2001) Development of oligonucleotide lateral-flow immunoassay for multi-parameter detection. J. Immunol. Methods 258, 73-84... 

Slinger, R., Milk, R., Gaboury, I., and Diaz-Mitoma, F. (2004) Evaluation of the QuickLab RSV test, a new rapid lateral-flow immunoassay for detection of respiratory syncytial virus antigen. J Clin Microbiol. 42, 3731-3733... 

Wang, S., Zhang, C., Wang, J., Zhang, Y. (2005) Development of colloidal gold-based flow-through and lateral-flow immunoassays for the rapid detection of the insecticide carbaryl. Anal Chim Acta. 546, 161-66... 

The reliability of the test strip immunoassay was determined by carrying out the test with the uncontaminated samples spiked with detected target at three levels and analyzed by strip test and instrumental analysis. The results obtained by strip test should be consistent with the results obtained by instrument. The correlation between the two methods should be good. An example of validation of gold-based lateral flow immunoassay and analysis of food samples for the detection of carbaryl was shown in the following. 

Matrix Spiked level (mg/kg) Results obtained by gold-based lateral-flow immunoassay (n = 3)a Results obtained by HPLC (mg/ kg)b... 

The tests used most frequently for speciation of animal products are the enzyme-hnked immunosorbent assay (ELISA), including immunosticks and, more recently, lateral flow immunoassays (LFIAs), the latter of which now use latex particles or colloidal gold for detection rather than the older enzyme immunoassay (EIA) technology (seeTable 13.1). 

Figure 5.3 Schematic representation of the mode of operation of a direct sandwich format lateral flow immunoassay showing test results for a compliant (negative) sample (a) and a non-compliant (positive) sample (b).

Commercial Lateral-Flow Immunoassays for Milk, Animal Tissues, and Honey... 

TABLE 5.4 Summary of Commercially Available Lateral-Flow Immunoassays for Detection of... 

O Keeffe M, Crabbe P, Salden M, Wichers J, van Peteghem C, Kohen E, Pieraccini G, Moneti G, Preliminary evaluation of a lateral flow immunoassay device for screening urine samples for the presence of sulphamethazine, J. Immun. Meth. 2003 278 117-126. 

Multiplex Lateral Flow Immunoassay Using SERS Nanotags as Analyte Labels... 

Nadanaciva S, Willis JH, Barker ML, Gharaibeh D, Capaldi RA, Marusich MF, Will Y (2009) Lateral-flow immunoassay for detecting drug-induced inhibition of mitochondrial DNA repb-cation and mtDNA-encoded protein synthesis. J Immunol Methods, 343, 1-12. 

Rundstrom G, Jonsson A, Martensson O et al (2007) Lateral flow immunoassay using europium (III) chelate microparticles and time-resolved fluorescence for eosinophils and neutrophils in whole blood. Clin Chem 53 342-348... 

One very prominent area, which is only rather loosely connected to pharmaceutical fields, but which is nevertheless an essential aspect of health-related research, and in which cellulose-based materials, namely different paper types, play a fundamental role, is the development of paper-based disposable point-of-care diagnostics tools and low-cost diagnostics tools [49-51], Although the concept of using cellulose-based materials as an essential part is not new as such—basically every commercially available lateral flow immunoassay (e.g., pregnancy tests) contains a specialized paper as an integral part—the development of devices completely made out of paper-like materials has revolutionized the field, and surprisingly simple but powerful devices made out of paper have been developed and tested rmder real conditions in field trials various assay formats have been realized, and it is expected that these devices will have an impact on health care systems due to their cost-effectiveness. 

The first lateral-flow immunoassay was developed in the form of latex-agglutination assay by Singer and Plotz in 1956." Since then, significant advancements have been made in the manufacturing of the lateral-flow strips for the detection of various diseases. This idea of detection is being implemented into various fields for early detection of cancer, treatment of infectious diseases like Human Immunodeficiency Virus (HIV), malaria, influenza, and many more. 

Figure 5.18 Lateral flow immunoassay (LFIA) strip with its components.

Lateral flow immunoassay (LFIA) is a special type of microfluidic test strip in which flow of liquid is governed by capillary forces. The chemicals required for detection are preimmobilized on the test strip and the detection is usually colorimetric, so that the results are visible using the naked eye. Because colorimetry provides qualitative results, electrochemical and other optical transductions have been used for quantitative detection of analytes. 

Zhu JM, et al. Simultaneous detection of high-sensitivity cardiac troponin I and myoglobin by modified sandwich lateral flow immunoassay proof of principle. Clinical Chemistry 2011 57 1732-8. http //dx.doi.org/10.1373/clinchem.2011.171694. 

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