Products intended for human diagnostics applications are designed for a multitude of purposes including the evaluation of samples to assess whether an individual has a particular illness or condition, monitoring a response to treatment, or identifying the presence of substances such as hormones or drugs of abuse. Sample types comprise whole blood, plasma, serum, urine, faeces, sputum and spinal fluid, as well as tissue samples from organs or tumours, amongst others.
Many different assay formats are employed for human diagnostics, and we have described the utility of immunocytochemistry, immunohistochemistry (IHC), ELISA and lateral flow immunoassays for diagnosis on our Veterinary Diagnostics page. Other methods which may be employed include RT-PCR, immuno-PCR and the growth of microbiological cultures:
Real-Time Polymerase Chain Reaction (RT-PCR)
RT-PCR is an ideal technique for the rapid detection of pathogens in clinical samples, and is particularly useful for identifying those organisms which are difficult to culture. The reaction relies on a simple, three-stage cyclical procedure to amplify a specific sequence of DNA, quickly resulting in over a million copies. Following initial heat denaturation of the DNA to separate the two complementary strands, the temperature is lowered to enable primers to bind; these flank the target sequence and act as starting points for DNA synthesis. The temperature is then raised to the optimal value for the chosen DNA polymerase, which functions to amplify the region of interest. By carrying out this cycle repeatedly, typically in the region of 25-35 times, multiple copies of the target DNA sequence are produced. Although traditional PCR is an end-point method, normally relying on gel electrophoresis followed by ethidium bromide staining to visualise the product, RT-PCR (also known as quantitative-PCR or qPCR) is considerably more powerful and links generation of the PCR product to fluorescence intensity, enabling data to be collected throughout the process as it occurs.
Immuno-PCR
Immuno-PCR delivers extremely high levels of sensitivity, often providing antigen detection down to picogram or femtogram levels, and can be employed as a diagnostic method for the identification of low abundance targets such as the presence of viral particles very soon after infection. This powerful technique combines the antibody-based specificity of an ELISA with the amplification that is afforded by RT-PCR through the incorporation of an antibody which has been directly conjugated to an oligonucleotide. Once binding of the antibody-oligonucleotide conjugate to the target of interest has taken place, amplification of the oligonucleotide gives rise to a detectable DNA product. Immuno-PCR is most commonly performed as a sandwich assay format with a highly specific capture antibody bound to the wells of a microplate and the oligonucleotide-conjugated antibody used to complete the sandwich following antigen binding.
Growth of microbiological cultures
Microbiological cultures are regularly employed as a diagnostic method, and are used to detect the presence of viable microorganisms such as bacteria, fungi or parasites in clinical samples. Such cultures require the use of specialist media for the growth of specific microorganisms under controlled laboratory conditions. While a solid growth support such as agar is usually preferred for the detection of bacteria or fungi, which are capable of forming individual colonies, liquid cultures are often more useful for the detection of parasites since these do not generally form colonies in solid media.
BIOZOL offers an extensive range of products for human diagnostics applications, including PCR reagents, kits for the direct conjugation of antibodies to oligonucleotides, culture media, antibodies, blocking peptides, proteins, biochemicals, and more. These can easily be searched on the basis of species reactivity, application, clonality, host species and manufacturer using the selectable filters.
