Species-specific estimates of test accuracy were also performed with positive test results defined as those indicative of the specific species being considered, and a negative result was defined as the absence of any result indicative of that particular species (i.e., no bacteria present or presence of other bacterial species in the absence of the species being considered).
Brain death was generally defined as the hypoxic or ischemic changes indicative of neuronal necrosis, as assessed by a neuropathologist, that were seen during the autopsy.
Likewise, for milk, the sensitivity of the refractometer was defined as the probability of a test result indicative of inadequate milk total solids (<12%) as determined by spectrophotometry.
Specificity of the refractometer was defined as the probability of a test result indicative of adequate milk total solids (≥12%) as determined by spectrophotometry.
Specificity of the refractometer was defined as the probability of a test result indicative of an adequate colostral (≥50 g/L) or serum (≥10 g/L) IgG concentrations as determined by means of RID.
Occupation of the head of the household was defined as the job where the person spent the most time working in the past year, indicative of the main source of household income for the past year.
Age at onset was defined as the age at the time of the first manifestation of the disease or any neurological sign indicative of multiple sclerosis identified by a multiple sclerosis specialist neurologist.
Lower respiratory tract infection was defined as: the presence of wheezing, tachypnea, chest retractions, abnormal auscultatory findings (wheezing and crackles), the presence of fever, and radiologic evidence indicative of a LRI.
For each case, the time at the initial appearance of symptoms indicative of MS was used as an estimate of the disease onset, and the year in which this occurred was defined as the index year.
