A comparison of the polymerase chain reaction with standard laboratory methods for the detection of EHV-1 and EHV-4 in archival tissue samples.

The research article is about a study comparing the effectiveness of the polymerase chain reaction (PCR) to conventional laboratory techniques in detecting equid herpesvirus types 1 and 4 in stored horse tissue samples.

Methodology and Test Samples

• The researchers compared a system using PCR with histopathology and virus isolation methods in order to detect the presence of equid herpesvirus type 1 or 4 in horse tissues that had been submitted to a diagnostic laboratory.
• The tissues that were tested had been stored for up to 3 years.
• In total, 38 tissues representing 14 cases were embedded and stored in paraffin wax while 53 tissues representing 28 cases were stored immersed in a 10% formalin solution.

Results and Findings

• The analysis of the paraffin-embedded tissues using PCR resulted in predictive values of 1.0 and 0.91 for a positive and negative result respectively, with sensitivity and specificity values of 75% and 100% respectively.
• On the other hand, an analysis of the formalin-immersed tissues yielded predictive values of 0.44 and 0.42 for a positive and negative result respectively, with sensitivity and specificity values of 28% and 57% respectively.
• The poorer results from the latter set of tissues were attributed to contamination of samples during the wax-embedding process. Additionally, it was found that viral DNA could not be amplified from older tissues.

Implications and Conclusions

• The study found that PCR is reliable when applied to tissues under appropriate conditions collected for routine diagnosis. However, its reliability decreases when multiple samples are managed collectively.
• Further, the research discovered that storing tissues in wax blocks for 14 or more years impedes the subsequent amplification of viral DNA from these tissues. This could potentially limit the application and efficiency of PCR in routine laboratory diagnosis when dealing with older samples.
• The implications of these results highlight that the operations process within laboratories needs careful consideration when using PCR for detection of EHV-1 and EHV-4 in tissue samples.