Why is mid-day urine preferred over first morning urine?

First morning urine is the most concentrated urine of the day — it has been accumulating in the bladder overnight and is richest in urinary waste products. While this can be useful for some urine tests (pregnancy tests, nitrites for UTI), for OncuraKit's miRNA test it can introduce higher levels of cellular debris, bacteria, and degraded cellular material from overnight bladder residence. Mid-day urine — collected 2–4 hours after your last urination — represents fresh, filtrate-rich urine with more representative miRNA content from the kidneys. The Yenos studies established the HL reference range using mid-day urine collection protocol, and the 1.5× HL threshold is calibrated for this collection timing.