All participants participating in 1A Visit 2 and 2A Visit 2 handed in urine samples that they collected themselves in a urine container. A subset of urine samples were immediately used for standard urinalysis. The remaining samples were placed into long term storage for future analyses.

Depending on the participant, one of the following urine samples were collected:

• A 24-hour urine sample is a standard urine collection protocol for adults. Urine is collected in a special container over a full 24-hour period. The container must be kept cool until the urine is returned to the lab. All 24-hour urine containers must be received by the laboratory within 24 hours after collection is completed
• A timed overnight urine sample is collected from underage participants. Urine was collected during a 12-hour period, starting from 8pm the night before until 8am of the morning of the Lifelines visit.
  
• A first morning urine sample is the most concentrated and the most likely to detect abnormalities. Participants emptied their bladder before lying down to sleep, did not urinate during the night, and collected one to two ounces of their first urine from the first urination in the morning in a clean container. The first 60.000 adult participants of assessment 1A handed in a first morning sample, but this practice was discontinued as it was experienced as inconvenient.

Participants were instructed to keep the urine sample cold until handing it in.

Aliquoting the urine sample. An aliquot is a fraction( 900ųl) of a specimen. Two different types of urine sampling:

1. Aliquot plain sample
2. Aliquot sample |EDTA/Asc.acid suspension]] added.

Using Synchron Urine Aliquoting Robot

Stored at -80°C