How Diagnostic Testing is Shaping the Field of Personalized Medicine

By Nicole Radford, VP of Laboratory Services, Florida Cancer Specialists & Research Institute

The diagnostic laboratory has always been an important partner to every clinician. Information gleaned from the work in the laboratory can assist in clinical decision-making, taking some of the “guesswork” out of the diagnosis process. Over the last several years, personalized medicine has taken center stage in healthcare, and diagnostics has been right there to provide the key information needed to take advantage of such cutting-edge tools.

Personalized medicine represents the use of a patient’s genetic makeup and profile to determine the prevention, diagnosis, prognosis, and treatment of various medical ailments. Just as healthcare has evolved and advanced through the years, so has the diagnostic tools used in the pursuit of such personalized medicine. Once considered something that was a “luxury” to be able to access, genetic testing has become much more attainable—and useful—to the clinical world.

One exciting use of molecular and genetic diagnostics is in pharmacogenomics. With specific genetic information, the clinician has the ability to provide more targeted therapy/treatment for the patient.

Thanks to the Human Genome project, molecular and genetic testing can provide a wealth of knowledge regarding many perplexing human ailments. Molecular testing provides insight into the key biomarkers and variants on a patient’s genome that may be affecting their health. This type of testing uses sequencing technology to access and analyze a patient’s genomic information. Next-Generation Sequencing (NGS) and Sanger Sequencing are arguably the most used methods in the molecular diagnostic world today, with each type of sequencing having their own pros and cons. The benefit of NGS testing is the ability to review a very large amount of genomic material at once (i.e., millions of DNA fragments simultaneously). Conversely, this type of technology may be found to be quite expensive, with a longer time from test request to result. On the other hand, Sanger sequencing reviews a single DNA fragment at a time, allowing concentration on and prompt resulting of a small number of genes with great accuracy. The disadvantage of this technology is that its low sensitivity leads to a decreased ability to recognize actionable mutations in a larger amount of genes.

Genetic testing uses the chromosomal makeup of a patient in the pursuit of better overall outcomes. Often used interchangeably with genomic testing, genetic testing uses cytogenetic methods such as karyotyping, fluorescent in-situ hybridization (FISH), and microarray to provide insight into a patient’s current (and maybe future) condition. Cytogenetics, one of the earliest diagnostic tests used in personalized medicine, utilizes various technical methods to identify the chromosomal material of the patients cells. This testing is often used to identify significant developmental disorders and congenital disabilities, as well as various types of hematological cancers (i.e., Leukemias). It is also a good tool for prognostics and treatment predictors. On the contrary, genetic testing does not account for single nucleotide variations that could be contributing to the identified condition. As such, it is suggested that it be used in conjunction with other complementary tools—such as molecular sequencing.

Like everything else in science, healthcare, and technology, the use of diagnostics in personalized medicine is continuously evolving. However, a few applications of diagnostics for this purpose has matured over the years of its prescriptive use.

Pharmacogenomics: One exciting use of molecular and genetic diagnostics is in pharmacogenomics. With specific genetic information, the clinician has the ability to provide more targeted therapy/treatment for the patient. In some specific cases, whether a patient will have side effects from a drug may even be determined with such testing.

Diagnosis: Perhaps the most common use of molecular and genetic diagnostics is to diagnose various conditions. As previously stated, a wealth of knowledge may be garnered when analyzing a patient’s genetic makeup. In conjunction with other clues (such as history and physical examination), identifying variants, biomarkers, etc., may paint a very clear picture of the patient’s health status. With this information, a clinician can more quickly begin the process of addressing the identified issues.

Predicting and Monitoring Prognosis: In addition to identifying issues, diagnostic testing can assist with predicting a patient’s prognosis. Specific mutations and variants are known to have a direct correlation to either a good or not-so-good outcome. Clinicians can use the advantage of this predictive value to help guide what they do with their patients. In addition to being used to predict future prognosis, these valuable tools can also be used to monitor the patient’s progress. Once the disease state is diagnosed, the appropriate test to monitor the progress of treatment may be determined. For example, the BCR-ABL1 Quantitative test by PCR may be used to monitor the progression of treatment for chronic myeloid leukemia (CML) by providing a logarithmic depiction of the patient’s status (as demonstrated by the test results). With this information in hand, a provider can determine if anything in the patient’s treatment plan needs to be adjusted.

Prevention: Risk stratification is another important use of diagnostic testing. Specific types of tests may be used as a means of screening for potential future issues. For example, what may be one of the most widely known tests is for the BRCA mutations that are linked to breast cancer. In 2013, a famous actress made it known publicly that she opted for a radical, prophylactic double mastectomy after testing positive for this mutation.

The use of diagnostic testing in personalized medicine has proven to be of great value. The information from such tools has great potential of contributing to the continued advancement of healthcare. As time and technology continue to progress, the power of such information will undoubtedly continue to grow in strength.