Home test strips for urinary tract infections (UTIs) offer a convenient screening method for individuals experiencing symptoms like burning or frequent urination. These strips detect chemical markers in the urine that signal the presence of an infection. They provide a quick, preliminary indication of whether a bacterial infection may be active. Understanding the color changes allows people to determine if they need to seek professional medical attention.
Direct Interpretation of the Purple Result
The appearance of a purple color on a specific pad indicates the detection of nitrites. This result is significant because nitrites are not normally present in healthy urine. Their presence is a chemical fingerprint left by certain bacteria.
Bacteria commonly associated with UTIs, such as Escherichia coli (E. coli), possess an enzyme that converts normal dietary nitrates (naturally found in urine) into nitrites. This conversion process is what the test strip captures.
A positive nitrite result, represented by the purple color, strongly suggests an active bacterial infection. A deeper or darker shade of purple generally correlates with a higher concentration of nitrites, indicating more extensive bacterial activity and growth.
Contextualizing Other Test Strip Indicators
While the purple color is a strong sign of infection, a complete analysis requires examining the other indicators on the strip. The test strip typically includes a separate pad to detect Leukocyte Esterase (LEU), an enzyme found in white blood cells (WBCs). Detecting LEU indicates that the body’s immune system is actively fighting inflammation within the urinary tract.
The leukocyte pad changes color differently than the nitrite pad, often appearing as a shade of pink or brown. When both the nitrite pad (purple) and the leukocyte pad show a positive color change, it creates the strongest indication of a UTI. The combined presence of bacterial markers (nitrites) and immune response cells (leukocytes) is highly suggestive of an active infection.
Test strips may also include pads for other substances, such as blood (hematuria) or protein (proteinuria). These indicators provide a broader view of urinary tract health, but nitrites and leukocytes remain the primary markers for infection screening.
Essential Next Steps Following Your Test
A positive result, particularly the purple color indicating nitrites, signals the need for immediate action. Home test strips are screening tools that identify the likelihood of an infection, not a definitive diagnosis. You must contact a healthcare provider promptly to confirm the results and obtain an accurate diagnosis.
The professional will likely perform a formal urinalysis or a urine culture to identify the specific bacteria. Confirmation is necessary because only a medical professional can prescribe the appropriate course of antibiotics. Delaying treatment can allow the infection to spread, potentially leading to serious conditions like a kidney infection.
Even if your test is ambiguous (e.g., positive leukocyte without nitrites) or if you have clear symptoms despite a negative test, seek medical advice. Some bacteria do not produce nitrites, meaning a negative nitrite result does not rule out a UTI entirely. Your healthcare provider can evaluate your symptoms alongside the test results to determine the necessary next steps.