A Philosophical Foundation for Diagnostic Blocks, with Criteria for Their Validation

BACKGROUND: In the absence of a suitable reference standard, diagnostic local anesthetic blocks cannot be validated in the manner conventionally used for diagnostic tests. Consequently, diagnostic blocks are vulnerable to criticism for lacking validity, or being "not proven." STUDY DESIGN: Philosophical essay. METHODS: Inspired by the "viewpoints" proposed by Bradford Hill for testing cause and effect in epidemiology, a set of axiomatic criteria was developed with which the validity of diagnostic blocks could be assessed. RESULTS: Eight criteria were established: plausibility, experiment, target-specificity, effect, duration, consistency, control, and replication. Applying weighted scores to these criteria produces a metric by which the validity of a particular diagnostic block can be quantified. CONCLUSION: The eight criteria provide an axiomatic, philosophical basis for diagnostic blocks in general, and serve to show what empirical evidence needs to be gathered in order to validate a particular block. The associated metric allows the scientific evidence for different blocks to be quantified and compared.