I previously discussed critical care summation score of the APACHE class the discussion on CITRIS-ALI. I you missed the discussion I present some of the basics of APACHE class scoring in sections 18-20. I was in training when they were introduced.
Prior to the 80s threshold thinking was widely discouraged as simplistic. Paulker embellished this approach with some goid concepts but the use of thresholds was too seductive. The growth of threshokd science (the use of guessed thresholds as gold standards in RCT emerged despite the fact that Paulker never advocate this expansive use of arbitrary thresholds.
Tiday I was in a fiscussion with a mathematician and I asked her why statiticians would think they could apply states to render an output statistically defining highly variable sets of guessed threshold combinations.
She said that mathematicians use tools which have been defined by proofs. So they may not think to explore the tool such as a SOFA score because they assume that it has been mathematically validated, that it is a sound tool mathematically.
So the introduction of the use of something as fluidic as SOFA as a primary endpoint in medical research pivotal to the survival of patients should be a wake up call.
The lesson is that it is not enough to do the math in the middle and leave the math at the two ends (the proximal gold standard and distal primary output) to the Pi.
If the gold standard or primary endpoint is presented as a function investigate the origin, validity reproducibility. and graphical behavior of the perceived function. If thresholds are used what was their origin and extent of rigor defining their behavior and reproducibility in the condition under test.
Biologic systems are often so complex that in the 20th century clinicians resorted to gross and often hierarchal averaging to get a signal. They were a little like a hiker with a cell phone wandering up the hill to get a signal. However the math derived from such wanderings must be considered with the signal and part of the equations defining probabilities not separate from them.
In the final analysis, If you haven’t studied these 20th century sores of the APACHE class then its probably best to start there first because yhose scores are not simply in the clinical domain (like an adverse occurance such as desth or a sibjective vlinical event such as a stroke). No these scores are in a continuum with the math which defines the clinical probability of efficacy which the PI is seeking to learn.