A proteinuria dipstick test is a screening tool used to detect elevated levels of protein in a urine sample. The kidneys filter waste from the blood while retaining substances like protein. When kidneys function normally, only a very small amount of protein is passed into the urine. A dipstick test provides a quick way to check for protein amounts that exceed the normal range. This is a preliminary screening, not a definitive diagnosis.
Performing the Test and Reading Results
The dipstick test strip has a color-sensitive pad with a pH indicator dye that changes color when it contacts protein in the urine. The process involves collecting a urine sample, briefly inserting the dipstick, and removing it. After a waiting period of about 60 seconds, the pad’s color is compared to a reference chart provided with the kit.
This chart displays a color scale corresponding to different protein concentrations. A “Negative” result indicates a normal or undetectable level of protein. A “Trace” result suggests a small amount of protein, which may not be significant. Further gradings, such as 1+, 2+, 3+, and 4+, represent progressively higher concentrations. For example, a 1+ result may correspond to 30 mg/dL of protein, while a 4+ can indicate 1000 mg/dL or more.
Understanding a Positive Result
A positive result on a dipstick test, known as proteinuria, indicates a higher-than-normal level of protein. A distinction is made between transient (temporary) and persistent (ongoing) proteinuria. A single positive test does not necessarily signal a serious problem, as several factors can cause temporary elevations. These benign causes include:
- Dehydration
- Strenuous exercise
- Fever
- Emotional stress
- Exposure to cold
Persistent proteinuria, where multiple tests over weeks or months are positive, can indicate underlying kidney issues. Conditions like diabetes and high blood pressure are common causes of chronic kidney disease. This condition damages the kidneys’ filtering units, allowing protein to leak from the blood into the urine. Problems during pregnancy, such as preeclampsia, can also cause proteinuria.
Accuracy and Follow-Up Testing
The proteinuria dipstick test has limitations. The test is most sensitive to albumin and may not detect other types of proteins, such as Bence-Jones proteins. Test accuracy can be influenced by several factors. For instance, highly alkaline urine (pH greater than 8.0) or contamination can lead to false-positive results. Conversely, very dilute urine can cause a false-negative result.
Due to these limitations, a positive dipstick test often requires confirmation with more precise methods. A healthcare provider may order a urine albumin-to-creatinine ratio (UACR), which is more accurate because it is less affected by urine concentration. Another common follow-up is a 24-hour urine collection. This test involves collecting all urine produced over a 24-hour period to measure the total amount of protein excreted daily. These tests help a doctor confirm persistent proteinuria and determine the appropriate course for diagnosis.