Table 3.

Summary of the effects of diurnal variation on CSF AD biomarkers levels.

Reference #	Demographics	Population size	Samples collection	Assay	Effects of diurnal variation
(60)	Non-demented subjects: 23–78 years old	15	6 ml CSF from lumbar catheter Each hour for 12, 24, or 36 h CSF frozen at –80°C after collection in polypropylene tubes	Aβ determined with ELISA	Aβ varied significantly, showing an increase over a 36 h period
(32)	Healthy subjects undergoing knee surgery	14	10–12 ml CSF from lumbar puncture Baseline, after 4–6 h, after 24 h CSF frozen at –80°C after collection in polypropylene tubes	Aβ42 determined with xMAP-based assay	No significant diurnal variation, slight decrease in Aβ42 levels that tended to return to baseline after 24 h
(62)	Mild stage AD patients: 59–85 years old; healthy volunteers: 64–77 years old	6 + 6	6 ml CSF from intrathecal catheter During 36 h, each hour CSF frozen at –80°C after collection in polypropylene tubes	Aβ42, t-tau, and p-tau determined with xMAP-based assay. Aβ40 determined with ELISA	No significant diurnal variation, less pronounced circadian pattern compared with the one in younger subjects
(63)	Patients suspected of having idiopathic normal pressure hydrocephalus (n = 9) or pseudotumor cerebri (n = 1)	10	40 ml CSF from lumbar catheter Every 6 h for 24 or 36 consecutive hours CSF frozen at –80°C after collection in polypropylene tubes	Aβ42, total tau, and p-tau181 determined with xMAP-based assay. Aβ40 determined with ELISA	No significant diurnal variation