Test strips, immunoassay

Wittmann, C. and P.-Y. Schreiter (1999). Analysis of terbuthylazine in soil samples by two test strip immunoassay formats using reflectance and luminescence detection. J. Agric. Food Chem., 47 2733-2737. 

Validation of the Test Strip Immunoassay by Comparing with Instrumental Analysis... 

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. 

Test strip and immunoflltration devices were developed by Ostermaier et al to detect sulfadiazine, sulfamethazine, and sulfamethoxypyridazine in milk. Direct competitive immunoassay was utilized with sulfonamide-horseradish peroxidase as the detector. The LOD for sulfamethazine for both the dipstick and immunoflltration was 10 pg kg for sulfadiazine, the LOD was 12 pg kg for the dipstick and 30 pg kg for immunoflltration. For sulfamethoxypyridazine, the LOD was 10 pgkg for the dipstick and 20 pgkg for immunoflltration. The devices were found to be suitable for on-site use with undiluted milk. 

A test strip enzyme immunoassay that could not discriminate between the 17 - and 17 -stereoisomers but allowed on-site screening of urine samples within 45-60 min was also reported (118). In this assay, 17, 19-nortestosterone was coupled to bovine serum albumin through a hemisuccinate bridge at the 17-position (119). This conjugate was used to raise polyclonal antibodies that would... 

The test kit is based on immunoassay techniques and the method takes about 10 minutes to provide an analysis. A unique tag, permanently attached to the polymer, changes the color of special test strips exposed to ppm levels of polymer. The strips indicate the amount of tagged polymer that is present, without interference from other additives and contaminants. This technology is not currently available for continuous inhibitor detection, but given the importance of AH Organic Programs, there is little doubt that further developments will take place. The Water Additives Division of Great Lakes Chemical Corp. have also recently introduced a similar simple and accurate immunoassay test for the detection of Belclene 200 antiscalent. 

Litman D, in Ngo T, Lenhoff H (eds) (1985) Test strip enzyme immunoassay. Enzyme-mediated immunoassay. Plenum Press 155-190... 

All patients with CKD and those with risk factors should be tested for albuminuria using an albumin-specific dipstick test. Since most dipstick methods are not specific for albumin, newer tests for microalbuminuria (30 to 300 mg/day) should be employed. Microalbuminuria test strips, such as the Chemstrip Micral-Test II strip, are optically read immunoassay-based methods. Here, the test strip is dipped into a urine sample and albumin present in the sample binds to gold-labeled antibodies. The detection field assumes a color ranging from white (0 mg/L) to red (100 mg/L). 

The first immunoassay performed in a capillary driven system was reported in 1978 [67]. Based on this technique, the commonly known over-the-counter pregnancy test was introduced into the market in the middle of the 80 s. Today, this microfluidic platform is commonly designated as a lateral flow test (LAT) [14]. Other terms are test strip , immunochromatographic strip , immunocapillary tests or sol particle immunoassay (SPIA) [68]. Astonishingly, hardly any publications from a microfluidic point of view or in terns of material classification exist, and apparently many company secrets are kept unpublished [69]. 

M.E. Ploum, W. Haasnoot, R.J.A. Paulussen, G.D. Van Bruchem, A. Hames, R. Schilt, F.A. Hug, Test Strip Enzyme Immunoassays and the Fast Screening of Nortesterone and Clenbuterol Residues in Urine Samples at the Parts per Billion Level , I. Chromatogr., 546, 413-427 (1991). 

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 lateral flow home pregnancy immunoassay shown schematically in the figure is a qualitative test for hcG. Urine is applied to the sample pad at the left end of a horizontal test strip made of nitrocellulose that serves as a wick. Liquid flows from left to right by capillary action. Liquid first encounters detection reagent on the conjugate pad. The reagent is called a conjugate because it consists of hcG monoclonal antibody... 

Immunoassays on Test Strips and other Planar Structures... 

Accommodation of a homogeneous separation-free immunoassay on a dry matrix. This is possible for SLFIA and for ARIS. Other possibilities are labeling with gold particles or liposomes. The art lies in contact-free accommodation of all the reagents on the test strip, in such a way that no immune reaction takes place during storage. 

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. 

Zhang FH, Yang SH, Kang TY, Cha GS, Nam H, Meyerhoff ME (2007) A rapid competitive binding nonseparation electrochemical enzyme immunoassay (NEEIA) test strip for microcystin-LR (MCLR) determination. Biosens Bioelectron 22 1419-1425... 

S168 Drost, R.H., Schultz, H.U., Maes, R.A.A. and van Rossum, J.M. (1987). A comparative study of a monoclonal immunoassay reagent strip test and high pressure liquid chromatography for theophylline. Clin. Toxicol. 25, 231-241. 

A growing application of the strip type of technology for immunoassay is for infectious disease testing and the rapid detection of various infectious antigens and antibodies including Chlamydia,group A streptococci, " Helicobacter pylori, ° infectious mononucleosis, and human immunodeficiency virus. These tests commonly use a lateral-flow format for urine, serum, plasma, or whole blood samples in conjunction with analytical techniques, such as enzyme immunoassay and immunochromatography. An alternative... 

As a POC (point of care) device semi-quantitative flow-immunoassay methods for the detection of antibodies or antigens had been developed and are well establish in e.g. pregnancy tests. This format is also known as strip test, one step strip test, immunochromatographic test, rapid flow diagnostic, rapid immunoassay or lateral flow immunoassay (LFI). The label is anyway a colored colloidal particle. Additionally to metal colloids, carbon (black) and silica or latex (various colors) are in use. 

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