Midstream urine and the humble dipstick.

The urine dipstick feels like a fixture of modern medicine. A slender strip dipped into a cup to absorb the urine sample with results read against a colour chart seconds later.

But its lineage stretches back further than most people realise, and understanding that history helps explain both its enduring usefulness and its very real limitations.

The urine dipstick was invented in the mid-19th century. The first test strips were created by Parisian chemist Jules Maumené in 1850, the primary purpose being to check urine for various diseases and infections. They were designed to detect the presence of specific substances in urine, which could indicate health issues.

Urine dipsticks are still used today, to test for:
• Glucose: Indicates potential diabetes
• Protein: May suggest kidney disease
• Ketones: Associated with diabetes or starvation
• Nitrites: Can indicate urinary tract infections
• Leukocytes: Suggests possible infection
• pH Levels: Helps assess kidney function and risk of kidney stones.

These tests allow for quick and effective monitoring of a patient’s health status but crucially, rely on an uncontaminated urine specimen.

Dipsticks today
Urine dipsticks are increasingly recognised as being less reliable for point-of-care urinary tract infection (UTI) diagnosis because they show low sensitivity, cannot distinguish between harmless background bacteria and active infection. They can yield frequent false-positive or false-negative results due to chemical interference, non-nitrate-reducing pathogens, or short bladder incubation times.[1]

Why midstream is important
All global guidelines stipulate midstream urine for routine UTI and prenatal screening.

This isn’t always easy as the instructions on NHS Patient Information website demonstrates, providing clumsy advice around midstream collection, including recommending using a jam-jar or disposable plastic cup with the contents then decanted into a “sterile container” if using a normal vessel is too difficult.[2, 3]

The Doctors’ Laboratory is more specific, advising that “Poor collection technique is the most common reason for a heavily mixed growth in a urine sample. It is almost impossible to collect a urine sample without any contamination from the normal bacterial flora which inhabits the area surrounding the urethral opening, but optimal collection technique will minimise this contamination and allow the true infective cause to stand out and be identified.”[4]

Today, the optimum technique for urine collection can be achieved using Peezy Midstream, the only device to automate midstream urine; precision engineering eliminates spillage, promotes hygiene, infection control and patient safety.

What actually happens on the strip, and why contamination matters
Each reagent pad on a dipstick relies on a chemical reaction that is sensitive not just to the analyte it’s designed to detect, but to a range of other things present in the sample, including extraneous material introduced during collection.

Contamination is the single biggest problem in real-world dipstick performance for women.

Because the urethral opening sits close to the vagina and perineal skin, a voided urine sample can pick up epithelial cells, vaginal flora, blood, discharge, or skin bacteria that have nothing to do with what’s happening in the bladder or kidneys.

This matters most for two dipstick components: leukocyte esterase and nitrite (the two analytes used as UTI surrogates), and the blood pad, which can register a false positive from menstrual contamination or vaginal spotting rather than hematuria.

Does a “precision” midstream specimen actually fix this?
The dipstick reacts to whatever chemistry is present in the collection vessel and it is unlikely to distinguish contaminating cells and bacteria from clinically significant ones. If a positive reading emerges – even from a contaminated urine specimen – empirical prescribing is recommended, which can fuel unnecessary antibiotic use and AMR I women.

So the intuitive answer is yes and clinical teaching has repeated the midstream, “clean-catch” instruction (initiate the stream, discard the first portion, catch urine only from the middle of voiding) for decades on the premise that it reduces contamination. Peezy Midstream has a solid evidence-base to demonstrate reduced contamination and mixed growth.

Implications for point-of-care women’s health diagnosis
The author has struggled to find any studies examining point of care dipstick analysis in Primary Care or Prenatal Settings. However, studies relating to elderly PoC testing for UTI conclude that: Dipsticks yielded limited clinical decision support compared with a symptom-driven approach in this study and were independently associated with excess antibiotics for UTI.5

This matters most where dipsticks are used as stand-alone decision tools, which is common in urgent care, primary care, and emergency settings for suspected UTI.

Studies comparing dipstick leukocyte and nitrite against urine culture (the actual reference standard) consistently show wide, and sometimes uncomfortable, gaps: sensitivity for leukocyte esterase has been reported anywhere from roughly 24% to 92% depending on the population under study and with nitrite typically more specific but far less sensitive, since not all UTI-causing organisms produce nitrite.

In other words, a negative dipstick does not reliably rule out infection. Furthermore, a positive dip (especially in an asymptomatic patient) does not reliably confirm it, particularly when the specimen may be contaminated.

The practical implication is that dipsticks work best as a triage tool in patients with a reasonably high likelihood of UTI, where both positive and negative results support lab culture for specific diagnosis and antimicrobial stewardship. High levels of empirical broad spectrum prescribing is arguably putting women on the frontline of AntiMicrobial Resistance (AMR).

What dipsticks mean for UTI diagnoses today
The dipstick remains in widespread use because it is cheap, fast, and viewed as useful as a triage tool, particularly in symptomatic patients or resource-limited settings where culture and lab-grade protein quantification aren’t readily available.

Here, the history is instructive: a technology designed in the 1950s to give clinicians a quick approximation at the bedside has, over decades, drifted into use as a quasi-definitive screening test in populations where its accuracy was never actually validated for that job.

The current evidence base is pushing practice back toward the dipstick’s original intent: a fast, low-cost adjunct that flags who needs a confirmatory lab test, rather than a replacement for one.
For point-of-care women’s health diagnosis specifically, that means treating a positive or negative dipstick as a prompt for clinical judgement and, where appropriate, culture or quantitative lab testing … but most of all, recognising that current recommended urine specimen collection has high contamination rates, creating a built-in source of error.

Where guideline midstream urine is recommended globally there remains no protocol to ensure its collection, leading to unreliable dipstick results and antibiotic prescribing to tackle infections that already carry 80-90% of antimicrobial resistant bacteria.

Without the right urine specimen, dipsticks are less likely to produce reliable results.

Without the right urine specimen, lab culture cannot always identify problem bacteria.

Without the right urine specimen, high levels of antimicrobial resistance can only increase in women.

The answer? Make midstream mainstream.

Further reading:
• Diagnostic accuracy of dipsticks for urinary tract infections in acutely hospitalised patients
• UTI in the elderly urine dipstick does not seem to be an appropriate tool …
• What is Leukocyte Esterase? Midstream urine specimen recommended

Sources
1. https://bpac.org.nz/bt/2013/june/urine-tests.aspx
2. https://www.nice.org.uk/guidance/ng109/chapter/Recommendations#treatment-for-women-with-lower-uti-who-are-not-pregnant
3. https://patient.info/mens-health/urine-infection-in-men/midstream-specimen-of-urine-msu
4. https://www.tdlpathology.com/specialties/microbiologyinfection-sciences/urine-culture-processing-and-results/
5. https://pubmed.ncbi.nlm.nih.gov/38997149/

AI was used in some sourcing of information and the editing of this article

© Giovanna Forte 2026