Discussion on the "negative value" of 24-hour urine protein test

Preface

Proteinuria is an independent risk factor for glomerular damage, tubular interstitial damage and chronic kidney disease, and has important value in predicting glomerular microthrombosis

Case history

The patient, male, 52 years old, routine urine analysis was qualitatively weakly positive for urine protein, and the urea and creatinine tests were normal

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case analysis

The 24-hour urine protein detection equipment is a Beckman (AU5821) automatic biochemical analyzer.

Studies have shown that 24-hour urine specimens have no effect on their urine protein test results after they are placed at room temperature (25°C).

Aminosalicylic acid, aspirin, barbiturates, etc.

Summarize

Collection and preservation of specimens

Collect a 24-hour urine specimen under the guidance of medical staff, and after mixing, take an appropriate amount of urine for examination and record the amount of urine

24-hour urine collection and retention method

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Precautions

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Selection of preservatives for 24-hour urine specimens

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Studies have shown ^[1] that under the condition of storage at 2-8°C, urine protein can be kept stable for 24 hours in 24 hours, and there is no significant change in the measurement results within 2 hours at room temperature, and the 24-hour results are significantly increased; formaldehyde will decrease by 24 hours.
Hourly urine protein measurement value, while xylene has no effect on the 24-hour urine protein measurement value
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Keep the urine for 24 hours for testing.
The urine specimen should be stored in a refrigerator at 2-8°C or preserved by adding 1mL/L xylene at room temperature
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The effect of adding preservatives and storage humidity on 24h urine protein detection

The commonly used preservative recommended for the 24-hour urine protein test is xylene, which forms a water-insoluble film on the upper layer of the urine.
Detection with a biochemical analyzer will reduce the result and easily cause blockage when the sample is added
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At the same time, toluene is a carcinogen and its purchase channels are limited
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Whether it is necessary to add preservatives for the quantitative detection of 24h urine protein, and to ensure the accuracy of the test results, has been confirmed by relevant clinical studies ^[2-3] .
Whether the 24h urine protein detection is preservative at 4℃, 25℃, 37℃ The results are not significant, but the results of urine specimens fluctuate more significantly when stored at 25°C and 37°C than at 4°C.
Therefore, the results of the test when stored at 4°C without preservatives are the best
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The effect of drugs on 24h urine test

The patient's materials have different effects on the urine test results
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Drugs that cause false negative results include: penicillin, cephalosporin, cephalosporin, etc.
; drugs that cause false positives include: quaternary ammonium salts, quinoline drugs, hydrogen peroxide, chlorpromazine, etc.
; albumin infusion will cause Urinary protein excretion will also increase
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Therefore, the patient's medication status should be considered when analyzing the test results
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The correlation between urine protein/urinary creatinine and 24-hour urine protein quantification

The 24-hour urine protein test specimens need to be collected for 24 hours, which is time-consuming and cumbersome.
Researchers at home and abroad ^{[4-6] have} used the stable excretion of human urine creatinine and found that the determination of urine protein/urinary creatinine is more effective than 24-hour urine protein quantification.
A good correlation is a good positive correlation
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The collection of urine protein/urinary creatinine test specimens is simple and fast, and the results are not subject to detection errors caused by difficulty in specimen collection and inaccurate urine output
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