Molecular Diagnostics
Quality controls are a critical part of the molecular diagnostic workflow for infectious diseases.
Molecular diagnostics is a set of laboratory techniques used to identify genetic material. This approach has revolutionized the field of laboratory medicine, enabling diagnosis and treatment of conditions—such as infectious diseases, cancers, and genetic disorders—more accurately and efficient.
Infectious diseases are illnesses caused by agents such as bacteria, viruses, fungi, and parasites. The detection of infectious agents using molecular tests can deliver results faster and, in some cases, more accurately than conventional methods. In addition, molecular diagnostics can provide vital information regarding the virulence, strain, and antibiotic resistance of the pathogen, which enables more informed treatment decisions.
Molecular Diagnostics of Infectious Diseases
The most common applications of molecular diagnostics of infectious diseases are in the diagnosis of viral (e.g., coronavirus, respiratory syncytial virus (RSV), and influenza) and bacterial (e.g., N. gonorrhoeae and C. trachomatis) infections. The following are common disease areas that utilize molecular tests:
- Healthcare-Associated Infections: These assays detect bacterial pathogens—including Clostridium difficile, Staphylococcus aureus, and MRSA.
- Gastrointestinal Infections: These assays detect bacterial and viral pathogens that are responsible for gastrointestinal infections—including Salmonella, Shigella, Campylobacter, Escherichia coli, Norovirus, and Rotavirus.
- Women’s Health and Sexually Transmitted Infections (STIs): These assays detect STIs—including Chlamydia, Gonorrhea, Human Papillomavirus (HPV), Herpes Simplex Virus (HSV), and Syphilis.
- Respiratory Infections: These assays detect viral and bacterial pathogens that are responsible for respiratory infections—including Influenza, SARS CoV-2, RSV, Adenovirus, Rhinovirus, and Human Metapneumovirus (hMPV).
Molecular Diagnostic Testing Workflow
The typical workflow of a molecular diagnostics test includes the following steps: nucleic acid extraction, amplification by polymerase chain reaction (PCR), and detection. Laboratories must follow strict quality control measures to ensure that each step performs as expected. This includes the use of two molecular controls: the appropriate internal/process control which is generally included with the test and external controls which are provided by a third-party manufacturer.
Internal Controls
Internal controls are used to monitor all steps of the molecular diagnostic workflow and can detect any contamination or inhibition of the reaction. They are included with each sample run on the test and are intended to help confirm the validity of the result for that specific sample. False-negative results can occur due to failures of any single step, so internal controls are important to ensure negative results are accurate.
External Controls
External controls, on the other hand, are run independently of the patient samples. They provide a reference that helps ensure the accuracy and reliability of test results. These controls contain known infectious agents or purified genetic material and are processed simultaneously with patient samples during testing. External controls are used to identify any errors or inconsistencies that may occur during testing, which may consequently result in false-negative or false-positive results.
Independent or third-party external quality controls are materials that have not been designed or optimized for use with any specific instrument, assay, or method. These controls provide an unbiased, independent assessment of assay performance which can help ensure the consistency and reliability of test results.
Molecular Diagnostics Have Revolutionized Healthcare
Molecular diagnostics has revolutionized healthcare by enabling accurate and efficient disease diagnosis and treatment. Its significant application in infectious disease detection includes the identification of genetic material from infectious agents using PCR technology. External controls are crucial for accuracy and reliability, ensuring effective treatment decisions and improved patient outcomes.