You have likely heard about mail-order genetic DNA testing kits. By providing a saliva sample you can receive a DNA analysis of the particular code in your cells that makes you unique. This consumer-facing diagnostic test, referred to by one startup as a genetic "service," has taken the world by storm in recent years. But John Howe, PhD , director of the molecular diagnostics laboratory at Yale School of Medicine, explains that these at-home kits cannot provide the level of detail and information that patients receive from a place like the Yale Center for Genomic Analysis.
Molecular diagnostics, also called molecular pathology, involves taking DNA or RNA, the unique genetic code found in our cells, and analyzing the sequences for red flags that can pinpoint the potential emergence of a specific disease. The field has expanded rapidly in recent years. Albert, H. Andrews, J. Environmental surveillance as a tool for identifying high-risk settings for typhoid transmission. Johnson Muluh, T.
Contribution of environmental surveillance toward interruption of poliovirus transmission in Nigeria, — Download references. You can also search for this author in PubMed Google Scholar.
Correspondence to Iruka N. Reprints and Permissions. The importance of molecular diagnostics for infectious diseases in low-resource settings. Nat Rev Microbiol 19, — Download citation.
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References 1. Article Google Scholar 2. Article Google Scholar 3. Article Google Scholar 4. For a colorimetric based analysis LAMP reaction mixture is added with hydroxynepthol blue HNB prior to amplification, thus avoiding cross contamination in the future Malik et al. Lin Yu et al. This technique was further coupled with a pH indicator, which helped in visual readout of the amplification reaction via color change in the reaction mixture Yu et al. LAMP technique avoids the use of costly reagents and instruments, thus helping in reducing the cost of diagnosis with rapid results Cascella et al.
Various studies have highlighted the application of LAMP technique in detecting coronavirus infections in patient samples Poon et al. Many other reports are also available on the use of LAMP as a diagnostic tool which includes the work carried out by El-Tholoth et al. This method can be carried out in closed tubes with either colorimetric or fluorescence detection. Their results are not only comparable to RT-PCR but also show 10 fold higher sensitivity when using purified targets Kashir and Yaqinuddin, After the first step, a second highly specific reaction initiated.
The challenge related to the LAMP method is the primer optimization and reaction conditions. Diagnosis of infectious diseases at the bed side of a patient where there is no need of sending patient samples to sophisticated labs is called as Point of Care testing POC. POC has a very important role to play during community contagious infections because it enables communities to diagnose infection without the complex laboratory infrastructure. POC testing is the only option for the remote areas of any community.
Xiang J. LFA is carried out on a strip which is a paper like membrane. The membrane has two lines coated on it among which one line contains gold nanoparticle-antibody conjugate and the other line contains a capture antibody. Patient samples are deposited on the strip. The strip draws proteins from the sample via capillary action. As the sample runs over the first line of the strip, antigen binds the nanoparticle-antibody conjugate.
This complex then moves to the second line where the capture antibody immobilizes the complex which makes a red or blue line visible on the strip. Individual gold nanoparticles on the strip are red, however clustered gold nanoparticles in solution show a blue color. These methods have comparatively less sensitivity than PCR and its variants. Based on the principle of LFA, some techniques are specifically developed to detect viral pathogens. This technique is very cost-effective and rapid in diagnosing viral pathogens.
It has been used for detecting Zika and Dengue virus in patient samples Gootenberg et al. A protocol has been developed by Zhang et al. It is a three-step diagnostic process. Isothermal amplification, detection and visual readout are the three steps of diagnosis which take less than an hour for the final results Zhang F. It has also reshaped the diagnostics of the current time. They play an important role in antiviral defense as the sequences are derived from bacteriophages which have previously infected bacteria Barrangou, This limits contamination because no separate pre-amplification and amplification is needed.
These complexes bind to corresponding sites closer to the primer recognition sites in the target sequence. In the study carried out by Xiong Ding et al. This assay could detect 1. This technique has been designed to perform simultaneous reverse transcription and isothermal amplification using RT-LAMP to the RNA extracted from nasopharyngeal swabs followed by Casmediated detection of virus. Some key advantages of this assay are isothermal amplification thus avoiding the need of thermocycling, easy to use systems like lateral flow strips, avoiding the use of complex laboratory infrastructure.
This technique can be easily mobilized to the hot spots of COVID transmission to ease the diagnosis process. A distinct approach in response to the increasing demand of global rapid testing for detecting SARS-CoV-2 infection was showcased by Rauch et al. This method is sensitive and a field deployable procedure to combat diagnosis crisis in pandemic situations.
The method is easy and can be used at minimal infrastructure sites. CREST uses easily available protein, low cost thermocyclers and easy to use fluorescent visualizers which makes it a very low cost and easily affordable diagnostic technique. An another portable, accurate and mobile phone based diagnostic assay was reported as an amplification free assay using Cas13a for directly detecting SARS-CoV The assay utilizes patient nasal swab to detect SARS-CoV-2 infection which can be analyzed with the help of a smart phone, this technology has made testing portable and affordable in the low resource areas.
It has exhibited limit of detection in 10 fM of RNA target. Using best combination of crRNAs for entire viral genome makes this assay best fit for point of care diagnosis Fozouni et al. A highly accurate, single nucleotide variant detection system developed by IGIB India employs Francisella novicida Fn-Cas9 based enzymatic readout for nucleotide detection and nucleobase identification.
Viral proteins as antigens or antibodies generated in response to viral infection can serve as the means of diagnosis in viral infectious diseases like COVID Relying on viral proteins for detection is cumbersome as the viral load fluctuates during the course of infection, so antibodies can better serve the diagnosis process To et al.
It has been an age old practice to detect specific antigens by antibodies that are directed against these antigenic epitopes using immunoblot assays Hartstein et al. However, there is a challenge of cross-reactivity between antibodies generated against SARS-CoV-2 and antibodies against other coronaviruses. A high frequency of cross reactivity was observed by a study carried out by Lv et al. According to a study carried out by Bin Ju et al. They observed the diverse antibody generation in the set of patients and proposed that such antibodies can serve as prophylactic and therapeutic strategies against COVID Ju et al.
Liu et al. The protocol used around 5 ml of fasting blood of every participant. C line appears when the sample is flushed over it. Study conducted by Zhao et al. The kit works on the principle of double antigen sandwich assay.
Elevated levels of C reactive-protein and D-dimer and low levels of lymphocytes, blood platelets and leukocytes were shown by Guan et al. DNA microarrays, sometimes called "gene chips," allow researchers to see the expression of hundreds or thousands of genes at one time. A DNA microarray is a thin-sized chip with thousands of single-stranded DNA fragments corresponding to various genes of interest that have been inserted into "spots" in the microarray.
A single microarray may contain 10, or more spots with each spot containing pieces of DNA from a different gene. A single gene chip can even hold representative fragments from the entire human genome.
Molecular diagnostics evaluates proteins in a cell, tissue, or organism, including the shape, function, and patterns of expression. Research seeks to identify proteins involved when normal cellular pathways support malignant growth. In cancerous tissue, some of the proteins critical for normal communication are damaged, inactive, overactive, or missing entirely. The full set of proteins disrupting cellular communications may vary from one cancer type to another, and they may also vary somewhat from one patient to another with that type of cancer.
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