Each stability pool combined specimens collected before and at several times after smoking. The experiment tested that mixture’s storage behavior, not the stability of every separate collection time.
Pools remained participant-specific
The investigators created one pool for each of fifteen participants from portions collected at −1.5, 1.5, 3.5, 5, 8, 10, 12 and 14 hours relative to administration. Pools were mixed and divided into aliquots for initial and later analysis.
Participants were not all combined into one shared pool, so the experiment retained some information about differences between individuals while averaging across their collection times.
Pooling changes the unit of inference
A participant’s pooled result cannot identify which original specimen contributed a later concentration change. It also cannot demonstrate that an early highly concentrated specimen and a late dilute specimen behave identically when stored separately. Those are different sample conditions.
Apply the evidence to the actual specimen
The study supports stability conclusions for authentic pooled oral fluid collected with the specified buffered device and stored at 4°C. It does not independently establish every time-specific storage profile. When discussing reanalysis, retain whether the case sample was pooled or individual and avoid turning the study’s participant-pool observations into guaranteed preservation of any saliva specimen.
Related reading: why stability conditions matter.
Research cited
Scheidweiler and colleagues (2016). Long term stability of cannabinoids in oral fluid after controlled cannabis administration. DOI: 10.1002/dta.2056.
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