So, the common types of genetic testing are single-site, single-gene analysis, and gene panel analysis. So, analysis of single site within a gene, so it's just a small portion, just one nucleotide change or something. And sequencing of one gene, exon, omni, or exon versus intron, and regulatory regions. Testing for family members with an identified mutation in a proband. So, this is good for cascade screening, because you already know a variant identified in a patient. So, the family members who are at risk of developing the same disease can be tested with this variant, just targeting this particular variant, and single-site analysis can be used. And if this comes back negative, this is a real true negative case for family screening, so this individual does not carry this variant, and we can be sure about that. Testing for a patient with a well-known single-gene disorder, such as sickle cell anemia or cystic fibrosis, you may just want to do one gene, and that's it, depending on the situation. It is often used for confirmatory testing for research genetic finding. So, research genetic finding always have to be confirmed by clinical testing. So, once you know where the variant is, or mutation is, you can just use a single-site or single-gene analysis. So, gene panel analysis is a simultaneous analysis of a group of disease-causal genes. Usually it's done with next-generational sequencing technology, so multiple genes can be sequenced simultaneously. So, testing for a patient with a disorder with multiple-causal genes, so it's always the case, one disorder, and locus heterogeneity, so you need to test multiple genes, because we don't know which gene is causing the disorder, so you can test the multiple-causal genes at the same time. Or testing for a patient with a family history of multiple types of conditional diseases, this happens in cancer syndrome. Some people may have pancreatic cancer, some people have GI cancer, but they may belong to one syndrome, and different types of cancer might develop in different individuals, so you can just test the panel testing. Instead of trying to target one gene at a time, panel testing can target multiple genes at the same time, and thus has a better chance of identifying the variants causing this cancer syndrome in the family. So, panel genetic analysis should be offered for patients who previously had a negative genetic test reload with a single-gene testing. This is always the case. Genetics is developing rapidly. Every year, things change, so over time, it's possible that novel genes are identified or novel technologies developed that retesting a negative result is a good thing with another methodology, so panel genetic testing should be offered if somebody comes back with negative prior years or several years earlier with just single-gene testing. I just wanted to mention several other gene genetic testing types so that you've heard it at least once. So, karyotype, I already kind of mentioned a collection of chromosomes lined up. It's very difficult to do the banding type, but spectrokaryotype is a multicolored probe hybridization-based method. It really comes up pretty, like different colors for different chromosomes, and you can line them up easily. Fluorescent in-situ hybridization, a FISH method, is to detect specific DNA sequence on a chromosome using a fluorescent probe, so you use this to see if there's a deletion of the section of a chromosome. I've used this before, so what happens is you have two chromosomes, and if the section of a chromosome is deleted, one would light up, the one without deletion, and one would not light up the portion without the deletion, so you know there is a deletion present in a particular chromosome. So chromosome microarray or molecular karyotype is a high-resolution method for detecting copy number alteration across the whole genome. So this method was not available when I was studying, but this method is amazing now that it's recommended for children with global developmental delay or intellectual disability. Often they carry deletion of certain pieces of chromosomes, so this is the method to go first for those individuals with developmental delay. Multi-ligation dependent probe amplification, MLPA, is another method to detect CNB copy number variation, but it's in a smaller segment of a gene or genes, and this is often used when you order for sequencing, you might need to test for if there's any CNB present in that region, so you can use MLPA to try to look, try to see if there's any CNB present. Methylation analysis is a methodology used for altered methylation for imprinting disorder that I described a little bit ago. So SNP microarray is the one that you may be a little more familiar with because it's the methodology used for genome-wide association studies, and they detect polymorphisms in the genome. So there's tons of polymorphisms, but you select certain ones and you make the SNP microarray and you use for studying certain populations, and this is the method used to study for polygenic disorders. So let's compare how different clinical and research genetic testing are. Both tests require process of informed consent, that doesn't change. Risks and benefits of the test should be explained. Potential consequence of the testing should be explained, yes. The main difference is that purpose of the test, who receives the results and payment process. So clinical testing is performed for clinical use. So results are used in decision-making for medical care. And the physician and the patient both receive, well, physician receives the test result first and then the results are relayed to the patient. And the payment usually is through insurance, the patient's insurance, or if it's not an in- it's not expensive. Sometimes self-pay may be cheaper to go, depending on what kind of testing it is. Some places do only charge $100 or a couple of hundred dollars for certain tests. But important to distinguish them. So research testing is a research purpose and the PI or investigator gets the results and payment process is covered usually by funding or some type of grant for research. So let's talk about pro, positive and negative of genetic testing. So having a definitive diagnosis can be a very believing experience for some patients who have gone through a lot to try to find out what it is. They, they, some patients go through so much before they can get the definitive diagnosis. So then, then they can, they may have a better understanding of health status and risks associated with it. Screening for other clinical manifestations is possible once the molecular defect is identified. Making informed medical decision and lifestyle decision is possible once the definitive diagnosis is made. And participation in clinical trials may be available for certain genotypes. So that allows them to participate in a certain clinical trials. And this is another thing is important is that identification with other at risk family members, especially children can be identified and preventative measure can be implemented prior to any disease manifestation. But definitely there are downsides to genetic testing. Negative means not all clear. So negative could be meaning that variant was benign. So it's basically negative. Or it could be that there was no variant identified because the target was wrong or methodology was wrong or methodology is not developed enough that we cannot detect the variant which is present. That's always possible. And there might be inconclusive or uncertain results. And those cases, cancelling is very difficult because, you know, they expected to find something and we weren't able to find anything, even with genetic testing. So results may alter their quality of life. They have to change their lifestyle, diet, restriction and activity basically for their lifetime because now that they have definitive diagnosis that certain things should be implemented to prevent a severe outcome. And even positive result may not provide clear prognosis. So we can provide historical information about certain genotype or genetic disorder. But we cannot definitively say you'll be developing this at age such and such. So we can give them as much information as we have currently with other patients in the history, but we cannot really predict what happens to this particular patient. And psychological effect of having a potentially incurable condition, that might be a big one too, that, you know, even though they may have thought that they have this condition, but now that, you know, genotype or mutation comes back positive, that they're kind of hit with, oh, I actually do have this condition because clinical diagnosis may not be as definite as molecular definitive diagnosis. And parental guilt about passing on a gene mutation. So I had this experience with a mother who did not even know that she had a genetic condition. And she had a child with severe cardiac malformation requiring multiple surgeries. And then we tested the child, found the mutation. But it happens that mother also carried the same mutation. But mother only had very, very mild learning disability, well, intellectual disability. That was it. She did not have anything else. So she felt very guilty. She didn't know that this was in her. And she passed that on to her child who had to go through multiple surgeries for heart. And she felt very bad. And the whole family was pretty distraught for finding this out. But, you know, there was nothing that she did wrong. So it's important that there is a great, you know, good support around the family so that they would be able to go through this period of finding the genetic defect. And hopefully, you know, there is enough support for every family member who goes through this. And a lot of times social workers are a great help in this kind of cases. Burden of notifying at-risk family members. So depending on family dynamics, it may not be easy to tell other family members about the finding of molecular defect. They may not even want to know about it. So it may create a difficult situation between family members. And, you know, hopefully, there could be some discussion so that all can agree on certain decisions. Some people may not want to know at all. So, you know, you just have to have a good discussion between the family members. But that may not be always possible. And financial issues is always a problem because finding genetic condition requires additional testing, follow-ups, and certain cases you may need special formula for babies. Some of the biochemical genetic disorder requires special formulas, which may not be covered fully by insurance. So families have to put up the cost on their own. And it's not a cheap formula because these are specially made, so they're expensive. So that adds up to additional financial burden to the family. So for these two social workers getting involved, and a lot of times, you know, try to get some kind of deal with companies, but it's not always easy to do because the insurance company is unlikely to cover for non-medical medications. These are like considered as a nutritional supplement.

genetic testing

single-site analysis

gene panel analysis

clinical genetic testing

research genetic testing