From the Guidelines
The ideal urine sample for specific investigations is a clean-catch midstream urine sample collected in a sterile container, with proper genital cleaning before collection, and stored appropriately to maintain sample integrity. For routine urinalysis and most common tests, a clean-catch midstream urine sample collected in the morning is generally preferred as it provides concentrated urine that has accumulated overnight 1. The timing of collection is also important, with first morning void being optimal for pregnancy tests, protein measurements, and metabolic disorder screening due to its concentration 1. For bacterial culture, a clean-catch midstream sample collected in a sterile container is essential to prevent contamination, with proper genital cleaning before collection 1. For 24-hour urine collections, all urine must be collected over a full day in a specialized container, often with preservatives 1. Random spot urine samples may be sufficient for urgent situations or certain tests like drug screening. Catheterized specimens are sometimes necessary for patients unable to provide voluntary samples or when contamination must be absolutely avoided 1. Proper storage, such as refrigeration for samples not immediately processed, and handling are crucial to maintain sample integrity and ensure accurate test results 1. Some key considerations for urine sample collection include:
- Collection method: clean-catch midstream or sterile urine bag 1
- Time and type: morning, random, or spot urine, with timed collection for certain tests 1
- Volume and void: midstream urine to avoid microbial contamination 1
- Collection device and container type: clean, leak-proof, and urine pH-range resistant 1
- Storage prior to processing: max 8 h before processing, with storage at 4°C or lower 1
From the Research
Ideal Urine Sample for Specific Investigations
The ideal urine sample for specific investigations is a midstream urine (MSU) sample, which is collected from the middle part of a void. This type of sample is recommended for adults and children who are continent and can empty their bladder on request 2.
Characteristics of an Ideal Urine Sample
- Collecting midstream specimens of urine (MSU) is a common nursing activity indicated for adults and children who are continent and can empty their bladder on request 2.
- Mid-stream urine was confirmed as the most appropriate sample, since the presence of contaminating elements, such as bacteria, analytes and formed particles are minimized 3.
- The general principle is to collect the midstream or middle part of a void if a urinary tract infection (UTI) is suspected 2.
Comparison of Urine Samples
- Counts of epithelial cells (EC), erythrocytes (ERY) and leukocytes (LEU) but not for cylinders (CAS) were significantly higher in the first-voided samples compared to mid-stream samples 3.
- A significantly higher count of EC, ERY and LEU was also observed between females and males in first-voided samples, whereas no significant difference could be found in mid-stream samples 3.
Collection Methods
- The mid-stream, clean-catch (MSCC) procedure for urine specimen collection is recommended to decrease contamination rates 4.
- However, a poster-based educational intervention with instructions on MSCC procedure failed to decrease contamination rates in an ED-based study 4.
Urine Culture and Infections
- Bacterial urinary tract infections (UTI) and some sexually transmitted infections (STI) can have overlapping signs and symptoms or nonspecific findings, such as pyuria on urinalysis 5.
- Infection with T vaginalis, N gonorrhoeae, or C trachomatis was not associated with having a urine culture yielding 10,000 or more colony-forming units per mililiter (CFU/mL) of bacteria compared with a urine culture yielding less than 10,000 CFU/mL or no urine culture obtained 5.