Paradigms and expectations: the nature of research and diagnostics

Moving molecular diagnostics from laboratory to clinical application: a case study using infectious pancreatic necrosis virus serotype A

AIMS

Using an RT-PCR method for detection of infectious pancreatic necrosis virus (IPNV) in Atlantic salmon as a model, this study examined the optimization and validation required to provide a method suitable for IPNV detection from fish tissue.

METHODS AND RESULTS

IPNV-positive Atlantic salmon kidney samples that had been titred or kidney spiked with IPNV were used. The amount of RNA in the reverse transcription (RT), RT denaturation temperature and incubation time, PCR annealing temperature and number of cycles were optimized. The optimized RT-PCR was able to detect IPNV in Atlantic salmon kidney calculated to have a titre of ten infectious units.

CONCLUSIONS

Extensive optimization is required to produce a PCR for detection of fish pathogens from methods designed in the laboratory.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study demonstrated some of the many variables that should be optimized before a fully validated assay can be claimed and illustrates the extensive validation required to fulfil requirements of the OIE and is of relevance to laboratories carrying out clinical testing.

Periodontal epidemiology: towards social science or molecular biology?

Terms such as 'molecular epidemiology' and 'genetic epidemiology' have been coined to depict the change from 'traditional epidemiology', concerned with disease determinants at the community or society level, over to 'modern epidemiology', which is concerned with determinants operating at the individual level or even below, i.e. at the organ, tissue, cell, or molecular level. In this commentary, we point out to the limitations of this development and suggest that more emphasis is placed on making the presumed causal disease models explicit, when investigating the relationship between putative determinants and disease. Understanding the disease processes at the micro-level is insufficient for understanding disease at the individual level; and disease patterns at the population level cannot be understood unless it is realized that individuals exist in a variety of contexts that cannot be reduced to individual attributes.

Molecular epidemiology: assumptions and limitations of commonly applied methods

An understanding of the epidemiology of a disease (i.e. its aetiology, transmission patterns) is crucial for the development and implementation of effective management practices. This requires sound epidemiological data. It is therefore important that scientists understand the assumptions and limitations of the methods used to gather such data. The aim of this paper is to discuss some of the assumptions and limitations of PCR-based methods used in studies of epidemiology. Since its development, PCR has had a major impact in the biological sciences. The ability to selectively amplify a specific region of the genome from a small amount of DNA makes this technique particularly useful as a diagnostic tool. A variety of PCR-based methods are available which can be used to identify strains and species of parasites. Some of these methods, such as random amplification of polymorphic DNA, have intrinsic properties which can limit their application. Other methods, such as PCR-restriction fragment length polymorphism, require the availability of a sound taxonomic or genetic framework for the development of any diagnostic system for a particular organism. The problems encountered developing diagnostic probes in the absence of such a framework will be discussed using Giardia intestinalis as an example.