Abstract
Objective-To develop a method of probability diagnostic, assignment (PDA) that uses continuous serologic measures and infection prevalence to estimate the probability of an animal being infected, using Neospora caninum as an example. Animals-196 N caninum-infected beef and dairy cattle and 553 cattle not infected with N caninum; 50 dairy cows that aborted and 50 herdmates that did not abort. Procedure-Probability density functions corresponding to distributions of N caninum kinetic ELISA results from infected and uninfected cattle were estimated by maximum likelihood methods. Maximum likelihood methods also were used to estimate N caninum infection prevalence in a herd that had an excessive number of abortions. Density functions and the prevalence estimate were incorporated into Bayes formula to calculate the conditional probability that a cow with a particular ELISA value was infected with N caninum. Results-Probability functions identified for infected and uninfected cattle were Weibull and inverse gamma functions, respectively. Herd prevalence was estimated, and probabilities of N caninum infection were determined for cows with various ELISA values. Conclusions and Clinical Relevance-Use of PDA offers an advantage to clinicians and diagnosticians over traditional seronegative or seropositive classifications used as a proxy for infection status by providing an assessment of the actual probability of infection. The PDA permits use of all diagnostic information inherent in an assay, thereby eliminating a need for estimates of sensitivity and specificity. The PDA also would have general utility in interpreting results of any diagnostic assay measured on a continuous or discrete scale.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 318-325 |
| Number of pages | 8 |
| Journal | American Journal of Veterinary Research |
| Volume | 63 |
| Issue number | 3 |
| DOIs | |
| State | Published - Mar 1 2002 |
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ASJC Scopus subject areas
- veterinary(all)
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A method of probability diagnostic assignment that applies Bayes theorem for use in serologic diagnostics, using an example of Neospora caninum infection in cattle. / Thurmond, Mark; Johnson, Wesley O.; Muñoz-Zanzi, Claudia A.; Su, Chun Lung; Hietala, Sharon K.
In: American Journal of Veterinary Research, Vol. 63, No. 3, 01.03.2002, p. 318-325.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - A method of probability diagnostic assignment that applies Bayes theorem for use in serologic diagnostics, using an example of Neospora caninum infection in cattle
AU - Thurmond, Mark
AU - Johnson, Wesley O.
AU - Muñoz-Zanzi, Claudia A.
AU - Su, Chun Lung
AU - Hietala, Sharon K.
PY - 2002/3/1
Y1 - 2002/3/1
N2 - Objective-To develop a method of probability diagnostic, assignment (PDA) that uses continuous serologic measures and infection prevalence to estimate the probability of an animal being infected, using Neospora caninum as an example. Animals-196 N caninum-infected beef and dairy cattle and 553 cattle not infected with N caninum; 50 dairy cows that aborted and 50 herdmates that did not abort. Procedure-Probability density functions corresponding to distributions of N caninum kinetic ELISA results from infected and uninfected cattle were estimated by maximum likelihood methods. Maximum likelihood methods also were used to estimate N caninum infection prevalence in a herd that had an excessive number of abortions. Density functions and the prevalence estimate were incorporated into Bayes formula to calculate the conditional probability that a cow with a particular ELISA value was infected with N caninum. Results-Probability functions identified for infected and uninfected cattle were Weibull and inverse gamma functions, respectively. Herd prevalence was estimated, and probabilities of N caninum infection were determined for cows with various ELISA values. Conclusions and Clinical Relevance-Use of PDA offers an advantage to clinicians and diagnosticians over traditional seronegative or seropositive classifications used as a proxy for infection status by providing an assessment of the actual probability of infection. The PDA permits use of all diagnostic information inherent in an assay, thereby eliminating a need for estimates of sensitivity and specificity. The PDA also would have general utility in interpreting results of any diagnostic assay measured on a continuous or discrete scale.
AB - Objective-To develop a method of probability diagnostic, assignment (PDA) that uses continuous serologic measures and infection prevalence to estimate the probability of an animal being infected, using Neospora caninum as an example. Animals-196 N caninum-infected beef and dairy cattle and 553 cattle not infected with N caninum; 50 dairy cows that aborted and 50 herdmates that did not abort. Procedure-Probability density functions corresponding to distributions of N caninum kinetic ELISA results from infected and uninfected cattle were estimated by maximum likelihood methods. Maximum likelihood methods also were used to estimate N caninum infection prevalence in a herd that had an excessive number of abortions. Density functions and the prevalence estimate were incorporated into Bayes formula to calculate the conditional probability that a cow with a particular ELISA value was infected with N caninum. Results-Probability functions identified for infected and uninfected cattle were Weibull and inverse gamma functions, respectively. Herd prevalence was estimated, and probabilities of N caninum infection were determined for cows with various ELISA values. Conclusions and Clinical Relevance-Use of PDA offers an advantage to clinicians and diagnosticians over traditional seronegative or seropositive classifications used as a proxy for infection status by providing an assessment of the actual probability of infection. The PDA permits use of all diagnostic information inherent in an assay, thereby eliminating a need for estimates of sensitivity and specificity. The PDA also would have general utility in interpreting results of any diagnostic assay measured on a continuous or discrete scale.
UR - http://www.scopus.com/inward/record.url?scp=0036521195&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0036521195&partnerID=8YFLogxK
U2 - 10.2460/ajvr.2002.63.318
DO - 10.2460/ajvr.2002.63.318
M3 - Article
C2 - 11911564
AN - SCOPUS:0036521195
VL - 63
SP - 318
EP - 325
JO - American Journal of Veterinary Research
JF - American Journal of Veterinary Research
SN - 0002-9645
IS - 3
ER -