Sensitivity and specificity of repeated test results from a commercial milk enzyme-linked immunosorbent assay for detection of Mycobacterium avium subspecies paratuberculosis in dairy cattle
Bibliographic record
Abstract
OBJECTIVE: To investigate the sensitivity and specificity of results of initial and repeated milk ELISAs (at 6- or 12-month intervals) to detect cows that were shedding Mycobacterium avium subsp paratuberculosis (ie, were infectious) and to evaluate factors influencing the probability that the results of a repeated milk ELISA would be positive for an infectious cow if the results of the initial milk ELISA were negative. DESIGN: Prospective cohort study. ANIMALS: 3,145 dairy cows from 32 herds. PROCEDURES: Herds from the 3 Maritime provinces in Canada (Prince Edward Island, New Brunswick, and Nova Scotia), participating in a Dairy Herd Improvement program, and that had undergone a prior Mycobacterium avium subsp paratuberculosis awareness project were selected for the study. Sample collection occurred between April 2009 and March 2011 with milk and fecal samples collected from all lactating cows in study herds every 6 months. Herds completing < 3 herd visits with collection of individual cow fecal or milk samples, within this sampling timeframe, were excluded from analyses. Fecal samples were cultured in liquid medium and a cow was defined as infectious if ≥ 1 sample was culture positive (reference test). A milk ELISA (index test) was completed with a commercial kit, following manufacturer's instructions. RESULTS: For a 6-month test interval, sensitivities of the milk ELISA to detect infectious cows were 22.0% and 32.6% for initial and combined initial and repeated tests (parallel interpretation), respectively. Specificity of the initial ELISA was 99.6% and was 99.2% for combined tests. For a 12-month test interval, sensitivities of the milk ELISA to detect infectious cows were 25.6% and 45.3% for initial and combined initial and repeated tests (parallel interpretation), respectively. Specificity of the initial ELISA was 99.6% and was 98.9% for combined tests. In infectious cows, magnitude of the initial negative ELISA result was a positive predictor for a positive repeated ELISA result. CONCLUSIONS AND CLINICAL RELEVANCE: Results of a repeated milk ELISA improved detection of Mycobacterium avium subsp paratuberculosis infectious cows, with minimal loss of specificity. A 12-month test interval provided a greater increase in sensitivity, relative to an initial test, than did a 6-month interval. Infectious cows with an initial negative milk ELISA result close to the cutoff for a positive test were more likely to have positive results on a repeated ELISA. Repeated testing improved detection of infectious cows and reduced risk of misclassification compared with a single ELISA result.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.005 | 0.016 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".