Chapter 2 · Dipstick and automated urinalysis QC

Urinalysis dipsticks require QC at each shift using positive and negative controls for key analytes: glucose, protein, blood, leucocytes, nitrite, and pH. Dipstick QC records must include lot number and expiry date. Automated urine analysers require the same QC process as other automated analysers. The laboratory must have documented criteria for when a dipstick or automated result requires microscopy confirmation.

Chapter 2 · Practical example

Dipstick QC — daily checks are not optional

Urine dipstick QC must be performed daily and whenever a new batch of strips is opened. A failed QC means all results from that batch are suspect.

▲ The situation

The laboratory receives a batch of urine dipstick strips with a new lot number. The section assistant opens the first tube and begins processing patient samples. No QC has been run on the new lot.

Reference: ISO 15189:2022 Clause 7.3.7

✓
Good practice

The section head stops result release from the new lot. A QC sample (a validated control material with known positive results for glucose, protein, leucocyte esterase, nitrite, and blood) is run on the new lot. The nitrite pad shows a weaker-than-expected reaction — the result is at the borderline of detection. The QC fails. The lot is quarantined, the supplier is contacted, and a replacement lot is requested. All patient results from the new lot are voided.

✗
Poor practice

Patient samples continue to be processed on the new lot. Over the next three days, 40 UTI samples are tested. Twelve samples that should have been nitrite-positive are reported as negative due to a batch defect. Several patients with UTIs are not identified and sent home without treatment. The batch defect is discovered when a clinician queries an unexpectedly negative result.

● What this means for your practice

A new batch of strips must be validated with QC before patient use — every time. Dipstick strips degrade and batch variability exists. QC failure on a new batch before it reaches patients costs one morning of investigation. QC failure discovered from patient results costs a recall review and missed diagnoses.