Parameters:
(1) 24 hour urine output in mL
(2) nocturnal urine output in mL (over an 8 hour period such as from 11 PM to 7 AM)
(3) age of the patient in years
ratio of nocturnal urine output =
= (nocturnal urine output) / (daily urine output)
Interpretation:
• For a young adult a ratio > 20% indicates nocturnal polyuria.
• For an elderly adult a ratio > 33% indicates nocturnal polyuria.
If we take a young adult as 20 and an elderly adult as 70, a possible line to determine the cutoff would be:
cutoff in percent =
= (0.26 * (age in years)) + 14.8
Performance”
• This is subject to many variables.
• The sleep interval within the 8 hours will strongly influence results.
• An average over several days is probably more reliable than a single result.
