Table 2.
Results from a generalized linear mixed model to analyse the variation in the magnitude of the IFN-γ response, (recorded as both PPD-B minus negative control and PPD-B minus PPD-A), subsequent to the IFN-γ disclosing event, in relation to the following explanatory variables: infection status at the capture event, time from the IFN-γ incident event, age, sex and source population, for 184 test events of 56 badgers captured in Gloucestershire between 2006 and 2012
| Response variable | Explanatory variables | Level | Estimate1 (SE) | F statistic2 | P value |
|---|---|---|---|---|---|
| PPD-B minus negative control | Infection status (reference level IFN-γ positive) | Stat-Pak positive | 0·38 (0·26) | F2,132·0 = 8·70 | < 0·001 |
| Culture positive | 1·07 (0·26) | ||||
| Time from the IFN-γ incident event (log transformed) | N/A | −0·15 (0·06) | F1,176·8 = 6·57 | 0·011 | |
| Age (reference level adult) | Cub | −0·47 (0·26) | F1,173·5 = 3·21 | 0·075 | |
| Sex (reference level female) | Male | −0·39 (0·15) | F1,45·0 = 6·76 | 0·013 | |
| Source population (reference level BVS) | WP | −0·10 (0·22) | F1,81·8 = 0·21 | 0·650 | |
| PPD-B minus PPD-A (B–A) | Infection status (reference level IFN-γ positive) | Stat-Pak positive | 0·37 (0·34) | F2,118·1 = 5·09 | 0·008 |
| Culture positive | 1·08 (0·34) | ||||
| Time from the IFN-γ incident event (log transformed) | N/A | −0·20 (0·08) | F1,175·1 = 6·38 | 0·012 | |
| Age (reference level adult) | Cub | −0·32 (0·36) | F1,176·9 = 0·78 | 0·379 | |
| Sex (reference level female) | Male | −0·29 (0·17) | F1,42·8 = 2·92 | 0·095 | |
| Source population (reference level BVS) | WP | −0·03 (0·28) | F1,105·8 = 0·01 | 0·914 |
Estimate from the model of the difference in the mean value relative to the reference level with its associated standard error (SE).
The test statistic from the model output with associated degrees of freedom.
Note: Significant effects are shown in bold, P < 0·05.
Abbreviations: BVS, Badger Vaccine Study; IFN-γ interferon-γ; PPD-A, purified protein derivative from Mycobacterium avium; PPD-B, purified protein derivative from Mycobacterium bovis.