Laboratory diagnostics

Urinalysis: A wealth of information in just a few drops

Easily available and affordable: A urine test can provide useful information about a variety of diseases and conditions.

Andrea Lutz

Published on September 4, 2023

Some experts even call what we excrete every day “liquid gold.” Find out what makes urinalysis so insightful, how the test works, what significance it has, and what role digitization is playing in the evaluation of these samples.

Why do doctors order a urinalysis?

In addition to a patient’s medical history and a physical examination, a urine test is an essential diagnostic tool in assessing a person’s health assessment. The test can be used to check the composition of a patients’ urine. A urinalysis alone usually doesn't give a complete picture, but the results provide information for further investigation and can help to diagnose various diseases of the urinary tract or kidneys as well as metabolic conditions. In addition, doctors can use it to monitor the progress of a disease and identify side effects.

Use cases for urinalysis at a glance

Routine medical evaluation such as standard annual screening and preoperative assessment, or screening for kidney disease, diabetes mellitus, and liver disease, among others

Assessing specific symptoms like abdominal pain, painful urination, fever, blood in the urine, and other urinary symptoms

Diagnosing medical conditions such as urinary tract infection, kidney stones, diabetes, and kidney inflammation

Monitoring disease progression: for example, diabetes-related kidney disease, blood-pressure related kidney disease, and kidney infection

Evaluating the response to therapy and pregnancy testing

How to perform a urine test optimally?

To perform a urine test optimally, you need to collect a clean urine sample from the patient. A clean urine sample is collected in a specimen cup (pee-in-a-cup method). Usually, only small amounts (30-60 mL) are required for urinalysis testing. Patients are often instructed to collect the sample midstream using the clean-catch method.

What is a clean-catch-method?

A “clean catch” aims to collect only uncontaminated urine. It refers to urine captured midway through urination.

Urinanalysis by using Atellica 1500 computer

In some situations, when patients cannot urinate naturally, other approaches are used, such as urethral catheterization or suprapubic aspiration. These are believed to provide the most reliable results because they minimize false positives. However, they’re invasive and painful. The urine bag method, where a sterile plastic collection bag is taped over the genitalia to collect urine, is an easy alternative that’s often used, but it has a higher error rate. Regardless of how the samples are taken, they are all analyzed by visual inspection and by chemical testing, if necessary (i.e., a dipstick test or laboratory method), or by microscopic examination. Not all samples require microscopic examination; in many cases, visual inspection with a dipstick may be sufficient. However, a comprehensive audit typically consists of three elements.

What is urethral catheterization and suprapic aspiration?

A urinary catheter is typically used when people have difficulty urinating naturally. The flexible tube is used to empty the bladder and collect the sample in a drainage bag.

Suprapubic aspiration collects a urine sample using a needle inserted into the bladder in the suprapubic region, typically to obtain an uncontaminated urine sample.

How to evaluate a urine sample

Visual exam
Microscopic exam
Dipstick test

During the visual exam, the urine is checked for color and clarity: Dark urine, abnormal colors, blood in the urine, and cloudy or foamy urine can indicate abnormalities.

The microscopic exam checks for the presence of solid elements in the urine like blood, epithelial or tumor cells, urinary casts, microorganisms, parasites, and crystals.

For the dipstick test, a thin strip with paper patches impregnated with chemicals is dipped into the urine. After a few seconds, these chemicals undergo a chemical reaction. If anything is abnormal, the patches change color. The clinicians measure these color shades against a standard chart to determine the findings.

What is evaluated in urine testing?

The quantity, color, and odor of the urine can already indicate possible health problems. That's why the visual inspection is important in addition to an examination of the chemical composition of the urine. Depending on a patient's initial situation, different variables of the samples can be tested like physical characteristics, including color, smell, sediment, and distinctive particles as well as its chemistry.

Urine is more than just a natural waste product. It’s a wealth of information for a clinician.
Will Hutt, Head of Primary Care, Decentralized Urinalysis & Acute Rapids at Siemens Healthineers

What substances do the colors on the dipstick represent?

In chemical tests, a thin strip commonly called a dipstick is inserted into the urine sample. A number of paper patches impregnated with chemicals are attached to the strip. These chemicals undergo a chemical reaction when certain constituents of the urine are present. The color change can begin to occur a few seconds after the strip has been dipped. Different test reactions occur at different time intervals. Therefore, the color changes are recorded at differing time intervals depending on the specific analyte. Currently, the following substances are chemically measurable on a routine test strip:

The components of urine

Each component of urine provides valuable information on biochemical processes in the body. [1,2]

: Urobilinogen is the end-product of conjugated bilirubin. Individuals with increased red blood cell destruction or liver disease may have elevated urobilinogen levels in their urine.
: Glucose in urine can indicate diabetes or high blood sugar, although it can also occur when glucose levels are normal: for example, during pregnancy or in cases of physiological stress.
: Bilirubin is a type of waste produced when old red blood cells break down. It can indicate liver disease.
: Ketones in urine emerge when the body begins to break down fat as a source of energy. Ketones may be a sign of uncontrolled diabetes or alcohol abuse.
: Specific gravity measures the kidneys’ ability to concentrate or dilute urine by comparing its density to that of distilled water. A high SG represents concentrated urine and may indicate dehydration.
: The presence of blood in the urine can occur for a variety of reasons, including lesions in the urinary tract, kidney stones, and tumors as well as systemic disorders such as tuberculosis.
: Urine pH is usually slightly acidic, though it can vary from as low as 4.5 to as high as 8.0 depending on the body’s acid-base balance. Kidney stone formation is highly influenced by urinary pH.
: Proteins in urine can indicate kidney disease or kidney damage. They may also be present in urine after strenuous exercise and when dehydrated.
: Nitrites in urine can indicate a bacterial infection. However, since not all bacteria produce nitrites, a negative nitrite test alone doesn’t rule out a urinary tract infection.
: Leukocyte esterase is an enzyme present in white blood cells. White blood cells in the urine may indicate inflammation of the kidneys or urinary tract due to bacterial infection.

Whenever a color on the strip changes, it provides information that helps to make clinical decisions. Sometimes small amounts of certain substances can be found in the urine in the absence of a medical problem, because some color values are more "normal" – depending on age, gender, medical history, and other factors – rather than being a cause for concern. However, not every color change is necessarily bad news. There can be contaminants and also normal levels of substances found in the urine.

Digitalization: Greater capacity to test more patients

Today, urine is one of the most common materials tested in clinical microbiology laboratories. Yet, the lack of standardized methodologies and variation due to manual observation can lead to inconsistent and unreliable results. Good news: Automated analysis is available, delivering faster results with consistent interpretation while decreasing the workload for frontline healthcare staff. That’s why digital urinalysis systems are an essential tool in the healthcare sector as the demand for point-of-care testing increases.

Digital urinalysis devices employ high-resolution cameras and powerful algorithms to analyze urine test strips. The device interprets the test strip's color and intensity, recognizes specific biomarkers in the urine sample, and displays the results on a digital screen. In a matter of moments, this method offers healthcare providers precise and reliable outcomes at the point of care.

Want to learn more?

Urinalysis becomes the gold standard and reaches beyond glucose testing. The ubiquitous urine test detects pregnancy to pH, bacteria to bilirubin, ketones to kidney function. From early warning of diabetes and kidney failure to population health management, urine testing helps doctors fight the world’s most threatening diseases.

Watch now on YouTube

Teaser image YouTube Documentary Ep 4 - Urine Good Hands

By Andrea Lutz

Andrea Lutz is a journalist and business trainer specialized on medical topics, technology, and healthcare IT. She lives in Nuremberg, Germany.

[1] https://www.nursingtimes.net/clinical-archive/continence/urinalysis-how-to-interpret-results-07-06-2016/

[2] https://www.hopkinslupus.org/lupus-tests/screening-laboratory-tests/urinalysis/#:~:text=Leukocyte%20Esterase%3A%20Leukocyte%20esterase%20is,tract%20due%20to%20bacterial%20infection