Estimating prior probability: The single prospective US cohort estimated that the prevalence of acute meningitis in populations presenting to the ED was ~1%. This slide illustrates the effect of a jolt accentuation test if a prior probability of 1% is assumed.
If the jolt accentuation test is negative, the posttest probability is quite low (< 0.1%). Most practitioners would consider this below their threshold for performing an LP and might choose not to perform additional testing. If the jolt accentuation test is positive, the posttest probability would be approximately 2%. One would have to decide whether this prior probability was high enough to warrant additional testing (ie, LP).
We also have to acknowledge that the jolt accentuation test has only been studied in a single setting and should be validated in more studies.