🩺 Urine Dipstick Testing

Urine dipstick testing is a rapid, point-of-care diagnostic tool used to detect biochemical changes in the urine. It involves the use of chemical reagent pads that change colour upon contact with specific substances like protein, glucose, ketones, blood, and inflammatory markers. It provides immediate clinical information regarding the renal, urinary, and metabolic systems. While highly useful for screening, positive results often require further laboratory confirmation via microscopy or biochemistry.

Urine dipstick testing is indicated for the screening and diagnosis of urinary tract infections (UTIs), monitoring of renal function (detecting proteinuria or haematuria), and metabolic screening (detecting glucose or ketones in diabetes). It is routinely performed during antenatal appointments to screen for pre-eclampsia and gestational diabetes. It may also be used in the investigation of abdominal pain, fever of unknown origin, or suspected drug toxicity/rhabdomyolysis (myoglobinuria).

There are no clinical contraindications to performing a urine dipstick, as it is a non-invasive bedside test. However, results may be uninterpretable or misleading if the patient is menstruating (leading to false positives for blood) or if the patient has recently consumed beetroot or medications like rifampicin which discolour the urine. It should not be used as the sole diagnostic tool for UTI in patients over 65, where asymptomatic bacteriuria is common.

The necessary equipment includes a fresh, mid-stream urine sample in a sterile specimen container, a bottle of reagent strips (checked for expiry date), clean gloves, a paper towel, and a timer or watch with a second hand. A clinical waste bin should be nearby for disposal of the used strip. Documentation charts or a patient record are needed to record the findings immediately.

Verify the patient's identity and ensure the sample is fresh and mid-stream. Check the dipstick bottle expiry date and donning gloves. Briefly immerse all reagent pads on the strip into the urine and remove immediately. Tap the edge of the strip against the container to remove excess urine. Hold the strip horizontally and wait for the time specified by the manufacturer (usually 30 to 120 seconds). Compare the colours on the strip to the reference chart on the bottle. Record the results accurately and dispose of the strip and urine in accordance with local clinical waste policy.

Leucocytes and nitrites are key indicators of UTI; nitrites are highly specific as they suggest the presence of Gram-negative bacteria like E. coli. Proteinuria may indicate intrinsic renal disease, pre-eclampsia, or may be transient due to fever or exercise. Glycosuria and ketonuria suggest uncontrolled diabetes or starvation. Haematuria always requires investigation to rule out malignancy, stones, or glomerulonephritis, especially in older patients. Bilirubin and urobilinogen pads help screen for hepatobiliary disease or haemolysis.

Using an expired container or one that has been left open for more than 6 months can lead to false readings. Failing to wait the specific 'read time' (e.g., 30 seconds for glucose, 60-120 seconds for leucocytes) may lead to inaccurate quantification. Over-saturating the strip and holding it vertically allows chemicals to 'run' between pads, causing cross-contamination of results. Failing to obtain a mid-stream sample (MSSU) often results in contamination with skin flora or vaginal discharge.

Briefly describe the urine appearance (e.g., 'clear and straw-coloured' or 'cloudy with a malodorous scent') before dipping. Wear gloves throughout and hold the strip horizontally after dipping to prevent cross-contamination. Explicitly state the time you are waiting for each pad, typically looking at the watch. Ensure you match the pad colours carefully against the scale on the specific bottle used, as different brands vary. Always offer to send the sample for 'Microscopy, Culture, and Sensitivity' (MC&S).

Relates to MLA 'Urinary tract infection' and 'Chronic kidney disease'. Students must know that for patients over 65 or those with indwelling catheters, dipsticks are unreliable for UTI diagnosis. In pregnancy, any degree of proteinuria requires further investigation for pre-eclampsia. Significant findings (blood, 2+ protein) usually necessitate follow-up with a formal laboratory Albumin-Creatinine Ratio (ACR) or Urine Culture.