State of Knowledge Regarding Transmission, Spread, and Management of Chronic Wasting Disease in U.S. Captive and Free-Ranging Cervid Populations (2025)
Chapter: Appendix D: Published Diagnostic Testing Platforms
Appendix D
Published Diagnostic Testing Platforms
This appendix serves a resource to summarize information on published chronic wasting disease (CWD) diagnostic testing platforms discussed in Chapter 4. The table describes the testing platform’s species and biological sample application, sensitivity, specificity, advantages, and limitations.
TABLE D.1 Summary of Published Diagnostic Testing Platforms, Comparing Diagnostic Sensitivity, Specificity, Advantages, and Limitations
| Diagnostic Test | Tissue | Species | Study Design | Se | Sp | Advantages | Limitations | References |
|---|---|---|---|---|---|---|---|---|
| IHC | Obex | MD, WTD, Elk | O, E | 77–100% | 100% | Highly specific; High Se in later stages of disease due to delayed central nervous system involvement | Lower Se as compared to peripheral lymphoid tissues, or to amplification assays; RPLN likely more sensitive than obex in WTD and MD | Spraker et al., 2002 Keane et al., 2008 Haley et al., 2009 Wyckoff et al., 2015 Miller and Williams, 2002 |
| RPLN | MD, WTD, Elk | O, E | 88–99% | 96–100% | Highly specific; RPLN likely more sensitive than obex in WTD and MD, especially in early disease stages; Biopsy can be used in official antemortem testing of WTD | Lower Se as compared to amplification assays | Miller and Williams, 2002 Keane et al., 2008 Haley et al., 2009 Picasso-Risso et al., 2022 Wyckoff et al., 2015 | |
| RAMALT | WTD | O | 68–80% | >99% | Highly specific | 3-month lag in detection as compared to RT-QuIC; Sample quality impacted by number of follicles obtained in biopsy; Lower detection odds in wt/G96S deer as compared to wt/wt deer | Keane et al., 2009 Thomsen et al., 2012 Henderson et al., 2020 | |
| Tonsil | MD, WTD | O | 93–99% | 100% | Highly specific; Biopsy can be used in official antemortem testing of WTD | 3-month lag in detection as compared to RT-QuIC | Spraker et al., 2002 Miller and Williams, 2002 Keane et al., 2009 Henderson et al., 2020 | |
| ELISA | Obex | MD, WTD, Elk | O | 92–93% | 100% | Rapid test; High level of agreement with IHC | Disagreement with IHC tends to be in early stages of disease | Hibler et al., 2003 |
| RPLN | MD, WTD, Elk | O | 98–100% | >99% | Rapid test; High level of agreement with IHC | Disagreement with IHC tends to be in early stages of disease | Hibler et al., 2003 | |
| PMCA | Obex | Elk | O | 95% | 94% | Higher Se as compared to IHC of obex and RPLN | Cross-contamination during sample processing can reduce Sp (down to 62%) | Wyckoff et al., 2015 |
| Tonsil | WTD | E | NA | NA | Higher Se in earlier stages of disease as compared to IHC | Se and Sp never formally estimated | Haley et al., 2012 | |
| Blood | WTD | O | 79.3% | 100% | 100% specificity with clinical disease | Low sensitivity (53%) in nonclinical, early stage (i.e., IHC+ lymph node only) disease | Kramm et al., 2017 | |
| Feces | WTD | O | 55–100% | 98% | Highly sensitive for animals at late stages of preclinical disease and wt genotype | Sensitivity decreases depending on the stage of the incubation period and polymorphic variations in the PRNP gene | Bravo-Risi et al., 2023 |
| RT-QuIC | RPLN | MD, WTD, Moose | O | 100% | 100% | May be more sensitive than IHC or ELISA at earlier stages of disease; Under evaluation for official test validation | Limited number of positive samples (n = 23, all MD or WTD) and comparison restricted to one tissue. Requires more validation studies to fully estimate Se and Sp in absence of a “gold standard” comparison | Haley et al., 2014 |
|---|---|---|---|---|---|---|---|---|
| Tonsil | WTD | O | 89–95% | 96–98% | Accessible for antemortem testing | Earlier detection as compared to IHC | Picasso-Risso et al., 2022 Henderson et al., 2020 | |
| RAMALT | WTD, Elk | O | 70–92% | 94–100% | Under evaluation for official test validation for antemortem testing | Lower Se in earlier stages of disease; Earlier detection as compared to IHC | Haley et al., 2016a Haley et al., 2016b Manne et al., 2017 Henderson et al., 2020 Piel et al., 2024 | |
| Ear pinna | MD, WTD | O | 81–95% | 91–100% | Easily accessible for antemortem testing | Mixed findings in regard to whether biopsy location on pinna affects Se | Ferreira et al., 2021 Burgener et al., 2022 | |
| Nasal secretions/brushings | WTD, Elk | O, E | 16–56% | 90–100% | NaPTA-precipitation enhanced Se (up to 56%) | Seeding activity and detection follows tonsil biopsy seeding activity; Highest sensitivity in terminal stages of disease | Kraft et al., 2023 Haley et al., 2016a Haley et al., 2016b | |
| Third eyelid | WTD, Elk | O, E | 72–96% | 100% | Higher Se as compared to IHC of same tissue | Lower Se observed in naturally infected elk; Low numbers of animals tested | Cooper et al., 2019 | |
| MN-QuIC | RPLN | WTD | O | 96% | 100% | Field-deployable testing equipment; Rapid turnaround time to test result | Low numbers of animals tested | Christenson et al., 2022 |
NOTE: Direct comparisons of sensitivity and specificity estimates reported across publications are complicated by differences in sample sources and numbers, study design, and potentially other variables. As a general pattern, results from different testing platforms and main tissue sampling sites tend to converge as disease progresses in infected individuals.
E: experimental study with samples collected from experimentally infected cervids; ELISA: enzyme-linked immunosorbent assay; IHC: immunohistochemistry; MD: mule deer; MN-QuIC: Minnesota-quaking-induced conversion (QuIC) assay; NaPTA: Sodium phosphotungstic acid; O: observational study with samples collected from naturally infected cervids; PMCA: protein misfolding cyclic amplification (PMCA) assay; RAMALT: rectoanal mucosa-associated lymph tissue; RPLN: retropharyngeal lymph nodes; RT-QuIC: real time quaking-induced conversion (RT-QuIC) assay; Se: sensitivity, defined as the probability of a CWD-positive cervid testing positive; Sp: specificity, defined as the probability of a CWD-negative cervid testing negative; WTD: white-tailed deer.
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