Immunoassay or Molecular Diagnostic
When considering these two methods, it is important to fully understand their advantages and disadvantages:
Advantages | Disadvantages | |
Immunoassays | Applications at point of care/need; Can identify individuals previously infected; Simple test procedure; Fast and low cost, low sample volume; High-throughput advantage over molecular-based methods; Broad sample opportunities, with no pre-treatment required, e.g. tears, saliva, sweat; Miniaturization of LFIA strips; scalable; Less protocol complexity (immunoassay-dependent), relevant across a range of settings; Scalable, facilitating large cohort/ population-wide testing; | Can be less sensitive than molecular diagnostics; Risk of false negatives; Usually designed for individual diseases, not for high-throughput screening of multiple targets; Require optimized antibodies to detect the antigen of interest which may limit the number of target antigens that can be detected; |
Molecular Diagnostics | Highly accurate and can be developed at speed; Uses primer designs from microbe sequences; potential for unlimited number of PCR/isothermal test designs once a sequence is obtained; Benefit from rapidly expanding databases of genome sequences which are readily available and accessible to researchers; Fewer false negatives (in some instances; deep nasal swabs result in fewer false negatives compared with other sampling methods, such as throat swabs or saliva); Newer molecular POC rapid tests offer lab-based performance with fast turn-around (<30 minutes); Allows monitoring of real-time disease progression; | PCR cannot discriminate dead from live bacteria or viruses, non-pathogenic from pathogenic strains, and is unclear regarding the persistence of infection; Test protocols are complex; Mainly suited to large, centralized diagnostic laboratories; Majority of molecular tests are used in CLIA labs with prolonged turnaround times: tests typically take 4–6 hours to complete; Changes in diagnostic accuracy occur over the disease course; |
Put assay choice into context
Immunoassays and molecular diagnostic tests are valuable tools in the fields of oncology and infectious disease diagnostics. Several factors should be considered before selecting the final diagnostic, starting with the intended clinical use and test performance (sensitivity, specificity, precision), along with the relative importance of speed, cost, resource availability, and yield. The clinical context of the assay is paramount when choosing whether to develop a molecular-based assay or an immunoassay, as are considerations of world market trends.
In the infectious disease and oncology settings, the performance of diagnostic tests should ideally be prioritized in terms of sensitivity and specificity. However, these may come at the cost of speed and throughput, and in the context of a pandemic or any highly infectious disease, the need for speed is often paramount. These seemingly contradictory requirements can be reconciled by the appropriate choice of molecular or immune-based assays. In general, molecular assays provide the sensitivity and specificity needed for accurate and reliable large-scale detection at the expense of speed. However, point-of-care (POC) molecular assays can provide higher sensitivity and specificity without compromising speed, producing results in 10-30 minutes. At the same time, POC immunoassays often provide speed with reduced sensitivity, as demonstrated by recent rapid antigen tests; however, those immunoassays that are compatible with high-throughput automated analyzer platforms can be as sensitive as molecular assays. Both methods tend to be compensatory in the infectious disease setting. Due to concerns about speed, immunoassays are an intuitive choice for diagnosis - however, there is still room for molecular diagnostics, and it is important to note that POC molecular tests are making significant advances to provide faster time to results.
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