A urine temperature strip is a thin, self-adhesive liquid crystal thermometer, typically integrated into the side of a specimen collection cup. The strip verifies the integrity and freshness of a urine sample by ensuring its temperature falls within the expected range of human body temperature at the time of collection. The technology relies on heat-sensitive liquid crystals, which change color in response to temperature fluctuations, providing an immediate visual reading. This initial temperature check is a standard procedure, serving as a primary defense against sample substitution or adulteration before laboratory analysis.
Proper Preparation and Placement of the Strip
The temperature strip must be correctly positioned against the container to ensure accurate heat transfer. In most cases, the strip is already affixed to the exterior of the collection cup, positioned so the liquid crystal panel is in direct contact with the urine inside. For strips that are not pre-attached, the adhesive backing must be pressed firmly against the outside surface of the cup, placing the sensing area below the minimum volume line of the collected specimen.
The strip must be fully submerged by the liquid sample for the reading to be valid. If the urine level is too low, the strip will not register the temperature, leading to an inaccurate reading. The temperature must be taken immediately after collection, as the urine begins to cool the moment it leaves the body, and any delay compromises the result. Improper placement or holding the cup near the strip with a bare hand can artificially alter the heat transfer, resulting in a misleading measurement.
Step-by-Step Interpretation of the Temperature Scale
The strip relies on thermochromic liquid crystals. As the urine temperature transfers through the cup wall to the strip, the crystals reflect specific wavelengths of light, causing the display to change color. The most common color scheme uses green to indicate the actual temperature, while other colors like tan or blue suggest temperatures just above or below the true reading.
To interpret the scale, locate the number displaying the most vivid green color, as this corresponds to the urine’s precise temperature. If a distinct green is not visible, the temperature is typically estimated to be midway between the numbers showing a tan or reddish-brown color and the numbers showing a blue color. For instance, if 94°F is blue and 96°F is tan, the temperature is likely between those two points. The clearest green indicator always represents the measured temperature.
Defining the Acceptable Temperature Range
The accepted industry-standard temperature range for a valid urine sample is typically set between 90°F and 100°F (32°C to 38°C) at the time of collection. This narrow window is based on the expected physiological temperature of freshly voided urine, which is slightly lower than the average core human body temperature of 98.6°F. This specific range confirms the sample’s authenticity, ensuring it was recently produced by the donor and has not been stored or manipulated.
If the temperature reading falls outside this range, the sample is flagged as suspicious and considered invalid for testing. A reading below 90°F suggests the sample was stored or diluted with cold liquid, while a reading above 100°F could indicate it was artificially heated. In such cases, the sample is usually rejected, and a recollection under stricter conditions may be required.
Common Factors That Invalidate the Reading
Several factors can compromise the validity of the temperature measurement. The most common issue is a delay in taking the reading, as the temperature is only considered accurate for a short period after collection, typically not exceeding four minutes. After this window, the natural cooling process to ambient room temperature can pull the reading below the 90°F minimum, falsely invalidating a fresh sample.
Environmental conditions also play a role. A very cold testing room can cause the sample to cool too rapidly, while a very hot room might keep a substituted sample warmer for longer. Touching the temperature strip or the collection cup near the strip with bare hands can artificially raise the local temperature, resulting in an inaccurately high reading. The collection process must strictly adhere to protocols that minimize these variables and ensure the reading is taken immediately.