URINALYSIS
Fig 2. Urine being tested by dipstick.
increase in the urine-specific gravity measurement potentially resulting in an incorrect diagnosis. Sample collection: Bacârea et al.5
noted
despite existing guidelines, the importance of the appropriate method for urine collection is not recognised by the patient and often not followed. Urine samples are not properly collected in more than half of cases even when they are previously instructed, and especially in elderly patients. Dipping technique: Incomplete dipping of the dipstick can occur when there is a small volume of sample available or owing to the dimensions of the urine collection device (Fig 2). Proper sample preparation: Including carefully wiping the edge of the dipstick immediately after immersing in urine to ensure application of the correct volume on each pad and to prevent cross- contamination between adjacent pads that is common in the standard dip-and- wipe method.6
Dipsticks with various There are limitations to consider when
carrying out dipstick urinalysis. Simerville et al.2
noted that “false-positive and
false-negative results are not unusual in dipstick urinalysis”. Time: Testing should be carried out within 1–2 hours of sample collection to give the most accurate results. If testing cannot be completed within this time samples should be refrigerated. Any bacteria or cells present in a urine sample kept at room temperature for more than one hour will continue to use glucose in the urine. This may result in a falsely decreased urine glucose measurement. Also, bacteria produce ammonia, which makes the urine more alkaline. Finally, this increase in urine pH causes cells, like white blood cells, to degrade and may become unrecognisable.3
Froom et al.4 discovered that
processing large numbers of urinary samples that arrive late afternoon can lead to overnight refrigeration. After storage approximately 25% of the leucocyte esterase-positive samples were less reactive. Precision of haemoglobin retests was also high but declined significantly after storage for 24 hours. Urine protein values increased after storage. After refrigeration for 24 hours, there is a risk of false-positive results for protein, false-negative results for leucocytes and erythrocytes. Temperature: Urinalysis should be performed on room-temperature urine. If a sample has been refrigerated, it should be allowed to sit at room temperature for 30 minutes before performing the urinalysis.. Cold urine can cause a false
Testing should be carried out within 1–2 hours of sample collection to give the most accurate
results. If testing cannot be completed within this time samples should be refrigerated
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WWW.PATHOLOGYINPRACTICE.COM February 2026
volumes deposited onto each pad; using the incorrect volume to wet the dipstick pads can lead to erroneous results. Correct interpretation of gradient colour scale: Interpretation of the gradient colour scale often requires the user to differentiate between various shades of the same colour, a difficult task for many people that can be exacerbated in certain lighting conditions. Additionally, the tests are inherently unreadable to users who are colour-blind.7 Precise readout timing: Each pad of the dipstick must be read at a specific time to ensure accuracy, as the results vary over time. Several of the pads have the same readout time, requiring the user to interpret several colour results simultaneously. Furthermore, many of the other readout times are close together (within 10–30 seconds), so the user must be able to quickly determine the results to maintain precise readout times.7 Degradation of reagents: A study by Crolla et al.8
of urinalysis depends upon the integrity of the test strips used. False results and diagnoses can arise from degradation of test-strip reagents through humidity, agnostic to brand. Although dipstick manufacturers state the capped vials containing the dipsticks must be closed immediately after removal of a strip, this recommendation may not always be followed in a busy department (Fig 3). Gallagher et al.9
discovered that after
exposure to air for a week, one third of the dipstick nitrite tests gave false-positive readings. At the end of a second week, nearly three quarters gave false-positive readings, a specificity of only 28%. Cohen10 investigated the impact of air exposure on
highlighted that the accuracy
Freepik
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