Introduction
Urine dipstick analysis is one of the most commonly performed bedside tests in clinical medicine and a high-yield OSCE skill. A dipstick can be performed in under two minutes yet generates information relevant to renal, metabolic, infective, and haematological diagnoses. In OSCE stations you may be asked to perform the test, interpret a pre-printed result card, or explain findings to a patient.
Performing the Dipstick
- 1Confirm a clean-catch midstream urine (MSU) sample is available — ideally collected into a sterile pot
- 2Check the expiry date on the dipstick container and that sticks have been stored correctly (away from moisture and heat)
- 3Immerse the dipstick fully in urine for no more than 2 seconds, then remove and hold horizontally
- 4Blot excess urine on the container edge — do not shake
- 5Read each pad at the correct time interval (typically 60–120 seconds — check the container)
- 6Compare pad colours to the reference chart in adequate lighting
- 7Document results and send MSU for microscopy, culture, and sensitivity (MC&S) if indicated
💡 Tip
Always inspect the urine visually before dipping: cloudy urine suggests pyuria or phosphaturia; red/brown suggests haematuria or myoglobinuria; dark yellow-green suggests bilirubin. Visual inspection is part of a complete urinalysis.
🧠 Mnemonic
PINK BUG — The Dipstick 7 Parameters
P — Protein (glomerular disease, UTI, pre-eclampsia, orthostatic)
I — Infection markers: leucocytes + nitrites together = UTI
N — Nitrites (gram-negative bacteria reduce nitrates to nitrites)
K — Ketones (DKA, starvation, prolonged vomiting, pregnancy)
B — Blood / haematuria (stone, malignancy, UTI, trauma, glomerulonephritis)
U — Urobilinogen (haemolysis, hepatocellular disease — raised; cholestasis — absent)
G — Glucose (hyperglycaemia >10 mmol/L, Fanconi syndrome, pregnancy)
Leucocytes and Nitrites
| Leucocytes | Nitrites | Interpretation |
|---|---|---|
| Positive | Positive | UTI highly likely — treat empirically, send MSU |
| Positive | Negative | UTI possible; also interstitial nephritis, TB, Chlamydia (does not reduce nitrates), contamination |
| Negative | Positive | Nitrites may persist; repeat with fresh MSU |
| Negative | Negative | UTI unlikely (high negative predictive value) |
💎 Clinical Pearl
Nitrites are only produced by gram-negative bacteria (E. coli, Klebsiella, Proteus) — gram-positive organisms such as Staphylococcus saprophyticus and Enterococcus do NOT produce nitrites. A leucocyte-positive, nitrite-negative dipstick in a symptomatic woman still warrants empirical treatment.
Protein
Normal urine protein is less than 150 mg per 24 hours — dipstick registers positive at approximately 300 mg/L.
| Protein Result | Clinical Significance |
|---|---|
| Trace | Likely benign — orthostatic (check early morning sample), fever, exercise |
| 1+ (0.3 g/L) | UTI, early renal disease, pre-eclampsia — investigate further |
| 2+ (1 g/L) | Significant proteinuria — check spot PCR or 24-hour urine |
| 3+ (≥3 g/L) | Nephrotic-range proteinuria — urgent nephrology referral |
Causes of significant proteinuria include: nephrotic syndrome, nephritic syndrome, diabetic nephropathy, pre-eclampsia, and UTI.
⚠️ Red Flag
Any proteinuria in a pregnant woman should be taken seriously. Proteinuria ≥1+ with hypertension (BP ≥140/90 mmHg) meets the diagnostic criteria for pre-eclampsia — this requires urgent assessment. Do not dismiss it as a UTI without measuring blood pressure.
Blood (Haematuria)
Dipstick blood detects haemoglobin — it does not differentiate between red blood cells (true haematuria), free haemoglobin (haemolysis), or myoglobin (rhabdomyolysis).
| Haematuria | Interpretation |
|---|---|
| Micro (non-visible) | Confirm with microscopy — >3 RBC/HPF on two consecutive samples is significant |
| Macro (visible) | Always warrants investigation — 2WW referral if >45 years and unexplained |
| Trace in menstruating female | Likely contamination — repeat after menstruation |
⚠️ Red Flag
Non-visible haematuria aged ≥60 (or ≥45 with risk factors: smoking, cyclophosphamide, occupational exposure) should be referred on the 2-week-wait pathway to exclude bladder, renal, or urothelial malignancy. Do not reflexively attribute haematuria to UTI without investigation.
Ketones
Ketones appear when fat metabolism is the predominant energy source:
- Diabetic ketoacidosis (DKA): large ketones with glycosuria and hyperglycaemia — a metabolic emergency
- Starvation ketosis: small to moderate ketones, no glucose
- Alcoholic ketoacidosis: ketones with low or normal glucose, history of excess alcohol
- Prolonged vomiting or fasting
- Pregnancy: physiological tendency to ketosis in first trimester
Glucose
The renal threshold for glucose is approximately 10 mmol/L. Glycosuria above this threshold suggests:
- Diabetes mellitus: most common — check HbA1c and random glucose
- Pregnancy: lower renal threshold — gestational diabetes must be excluded
- Fanconi syndrome: proximal tubular dysfunction — glycosuria with normal blood glucose
Urobilinogen and Bilirubin
| Parameter | Raised | Absent |
|---|---|---|
| Urobilinogen | Haemolysis, hepatocellular jaundice | Obstructive jaundice |
| Bilirubin | Conjugated hyperbilirubinaemia (hepatic, obstructive) | Not filtered when unconjugated |
Putting It All Together — Common OSCE Scenarios
| Scenario | Dipstick Pattern |
|---|---|
| Lower UTI | Leucocytes +++, Nitrites +, Blood +/- |
| Pyelonephritis | As above, plus protein +; systemically unwell |
| Nephrotic syndrome | Protein +++, Blood +/-, no leucocytes |
| DKA | Glucose +++, Ketones +++, Blood +/- |
| Bladder carcinoma | Blood +++, protein +/-, no leucocytes |
| Pre-eclampsia | Protein ++ or more, check BP |
| Rhabdomyolysis | Blood +++ on dipstick, few RBCs on microscopy |
FAQs
"Why might a dipstick show blood without true haematuria?"
The blood pad detects haemoglobin and myoglobin. Free haemoglobin from haemolysis and myoglobin from rhabdomyolysis both give a positive result without true red blood cells in the urine. Microscopy is essential to distinguish these — in rhabdomyolysis you will find few or no red cells despite a strongly positive dipstick for blood.
"How do I confirm a UTI after a positive dipstick?"
Send a midstream urine (MSU) for microscopy, culture, and sensitivity (MC&S). Growth of ≥10⁸ organisms/L with a pure growth of a recognised pathogen, combined with compatible symptoms, confirms UTI. Treat empirically based on local antibiograms while awaiting sensitivity results.
"When should I NOT treat a positive dipstick empirically?"
Do not treat asymptomatic bacteriuria in non-pregnant adults — this is an incidental finding that does not reduce complications and drives antibiotic resistance. Exceptions include pregnancy (treat all bacteriuria) and pre-urological procedure patients.
"What causes a falsely negative dipstick in a UTI?"
Dilute urine (specific gravity <1.005), very early infection before leucocyte accumulation, gram-positive organisms (no nitrites), refrigerated samples analysed cold, and expired dipstick sticks can all produce falsely negative results in a genuine UTI.
"What is the significance of proteinuria on dipstick during a routine check?"
Persistent proteinuria (positive on at least two separate occasions) warrants quantification with spot protein:creatinine ratio (PCR) or albumin:creatinine ratio (ACR), renal function tests, blood pressure measurement, and consideration of renal biopsy. Isolated transient proteinuria after exercise or fever is usually benign.
Related Posts
- Blood Results Interpretation OSCE — renal function, inflammatory markers, and LFTs to accompany dipstick findings
- A–E Assessment OSCE — managing sepsis triggered by pyelonephritis identified on dipstick
- Prescribing Safety OSCE — antibiotic selection and dose adjustment in renal impairment