Proteinuria: a ratio that nearly doubled, and a patient who did not change
Educational use only. Not clinically reviewed47-year-old woman for Comparison of the change against measurement variation, review of sampling conditions, review of the clinical picture, a matched repeat, and handoff of an owned treatment decision. About 60 simulated minutes.
What you will practise
- Compare the change against the variation the measurement carries.
- Read when and how each sample was taken as part of what it says.
- Check the patient against the number before acting on the number.
- Obtain the measurement that would actually answer the question.
- Transfer the finding with what it rests on stated.
Review and sources
Not clinically reviewed. No clinician has signed this scenario.
- Waikar SS, Rebholz CM, Zheng Z, Hurwitz S, et al. Biological variability of estimated GFR and albuminuria in CKD. American Journal of Kidney Diseases. 2018;72:538–546. doi:10.1053/j.ajkd.2018.04.023. Fifty clinically stable outpatients, cross-sectional, and the authors state the small sample limits the ability to detect differences. Reference change values describe measurement variation in a stable population; they are not a rule that a smaller change is meaningless in an unstable one.
- Fine DM, Ziegenbein M, Petri M, Han EC. A prospective study of protein excretion using short-interval timed urine collections in patients with lupus nephritis. Kidney International. 2009;76:1284–1288. doi:10.1038/ki.2009.344. Patients with lupus nephritis only, so the diurnal pattern may not transfer. The paper concludes by endorsing a 12-hour overnight collection as an excellent surrogate — it argues for better sampling rather than against sampling, which is the position taken here.
- Baba Y, Furuta I, Zhai T, Ohkuchi A, et al. Effect of urine creatinine level during pregnancy on dipstick test. Journal of Obstetrics and Gynaecology Research. 2017;43:967–973. doi:10.1111/jog.13327. A pregnant population at one institution with only twenty false-negative samples driving the comparison at p = 0.046. It shows an association between dilution and false negatives in that setting rather than establishing a general threshold.
Open Sim Lab is an educational simulator, not for clinical use. It is not a clinical decision-support tool, not a dosing calculator, and is not validated for any decision affecting a real patient.