Validation of laboratory tests for infectious diseases in wild mammals: review and recommendations

Abstract

Evaluation of the diagnostic sensitivity (DSe) and specificity (DSp) of tests for infectious diseases in wild animals is challenging, and some of the limitations may affect compliance with the OIE-recommended test validation pathway. We conducted a methodologic review of test validation studies for OIE-listed diseases in wild mammals published between 2008 and 2017 and focused on study design, statistical analysis, and reporting of results. Most published papers addressed Mycobacterium bovis infection in one or more wildlife species. Our review revealed limitations or missing information about sampled animals, identification criteria for positive and negative samples (case definition), representativeness of source and target populations, and species in the study, as well as information identifying animals sampled for calculations of DSe and DSp as naturally infected captive, free-ranging, or experimentally challenged animals. The deficiencies may have reflected omissions in reporting rather than design flaws, although lack of random sampling might have induced bias in estimates of DSe and DSp. We used case studies of validation of tests for hemorrhagic diseases in deer and white-nose syndrome in hibernating bats to demonstrate approaches for validation when new pathogen serotypes or genotypes are detected and diagnostic algorithms are changed, and how purposes of tests evolve together with the evolution of the pathogen after identification. We describe potential benefits of experimental challenge studies for obtaining DSe and DSp estimates, methods to maintain sample integrity, and Bayesian latent class models for statistical analysis. We make recommendations for improvements in future studies of detection test accuracy in wild mammals.

Suggested guidelines for validation of real-time PCR assays in veterinary diagnostic laboratories

“…This is discussed for assays pertinent to wildlife species in a companion article in this focus issue. 23 In the absence of knowledge about the true disease status, statistical methods can be used to estimate DSe and DSp. 21,30,47 Validating assays for wildlife often require alternative statistical methods, as reviewed in this focus issue.…”

“…B. To test the effect of concentrated co-targets, 10-fold dilution series of each stock target are spiked with a pool of competitor targets added at a strong concentration (20)(21)(22)(23)(24). The plate is extracted, and RT-rtPCR is performed.…”

“…21,30,47 Validating assays for wildlife often require alternative statistical methods, as reviewed in this focus issue. 23…”

The potential of diagnostic point‐of‐care tests (POCTs) for infectious and zoonotic animal diseases in developing countries: Technical, regulatory and sociocultural considerations

“…Disease investigation in wildlife presents unique challenges, due to often limited data on wildlife physiology and pathogen behaviour, as well as logistic and regulatory considerations around collection, use and international transport of wildlife and their tissues (OIE, 2018b ). A recent review from Jia et al ( 2020 ) about validation of laboratory tests for infectious diseases in wild mammals revealed incomplete or absent information about sampled animals and/or species, case definition criteria and source and target populations that would impact test validity and inform applicability of test results, including their status as naturally infected captive, free‐ranging or experimentally challenged animals. Sampling is often opportunistic, and individual capture and follow‐up frequently unachievable.…”

Experimental inoculation trial to determine the effects of temperature and humidity on White-nose Syndrome in hibernating bats

“…Research to determine whether management actions are effective at reducing disease effects can be challenging to conduct, especially in dynamic and complex ecological systems 4 . Controlled experiments are often used to determine disease susceptibility of hosts or quantify aspects of host–pathogen-environment interactions 5 . Experimental inoculation trials in laboratory settings provide the advantage of controlling and randomly assigning specific conditions of interest to enable causal inference and determine disease susceptibility.…”