Urinary Protein Plus Sign, Quantification, Creatinine Ratio, How Much Is Up To The Standard

Urinary protein is not only the result of kidney inflammation but also the cause of kidney cell death and kidney failure. Whether the urine protein is high or low largely determines whether the development and outcome of kidney disease are stable or develop into uremia.

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Some indicators of kidney disease need to be controlled within a certain range, such as creatinine, blood pressure, blood sugar, etc., too low or too high is not good.

For other indicators, there is no lower limit, such as urine protein, low-density lipoprotein cholesterol, and so on. Although a range with a lower limit is often marked on the laboratory test sheet, it is only a meaningless value randomly selected from the general population, and it is not the result of medical intervention. No matter how low it is, it can't be too high.

Of course, the indicators of healthy people can be very low, but it does not mean that the indicators of patients will drop very low. Each type of patient has a corresponding standard value and should not be overtreated.

1 How much urine protein is up to the standard?

24-hour urine protein quantitative examination is the gold standard for measuring urine protein leakage. The therapeutic goal of urinary protein is a 24-hour urinary protein quantity of less than 0.5g. Some tests are single urine, showing only plus (+) or minus (-), or urine protein/creatinine ratio. How to judge the plus and minus signs and urine protein/creatinine ratio? Don't worry, let's talk about the 0.5g standard first.

Why set the treatment target at 0.5g?

It followed up with patients with various urinary protein levels and found that patients with less than 0.5g had the best long-term outcome. Take nephritis patients with mild to moderate proteinuria as an example:

The General Hospital of the Eastern Theater Command has followed up on 1,000 patients with IgA nephropathy for 20 years and found that:

For patients whose 24-hour urinary protein quantity is less than 0.5g, almost no patients develop renal failure;

Renal failure occurred in about 20% of patients with 24-hour urine protein quantification between 0.5-1g;

About 70% of patients with 24-hour urine protein quantity of more than 1g developed renal failure.

IgA nephropathy accounts for half of the primary nephropathy and is the most representative. Let's look at membranous nephropathy, which is the most common type of nephrotic syndrome:

Kidney International (KI), an authoritative journal in the field of kidney disease, published a study that included more than 300 cases of primary membranous nephropathy and followed them up for 15 years:

1. Patients with long-term urinary protein below 0.3g have a high kidney survival rate, and almost no one develops uremia;

2. About 30% of the patients with urine protein between 0.3-3.5g and partial remission (half the highest value of urine protein) progressed to uremia;

3. About 70% of patients with long-term urinary protein above 3.5g developed uremia.

IgA and membranes account for 80% of primary kidney diseases, and the cut-off line for patients to obtain a good outcome is around 0.5g, so it is the target of treatment. It would be better if it can be reduced to 0.3g or below 0.15g, but it is not required.

2 Urinary protein plus and minus signs, how much is the standard?

It should be reminded that this comparison is premised: the patient's urine output is 1500ml throughout the day, which cannot be too different.

Because the urine routine is a single urine test, it is impossible to find out how much urine protein has been leaked throughout the day. It can only be inferred from the concentration of urine protein, that is, "thin" or "thick". In this comparison table, the default is urine with a urine volume of 1500ml and a medium dilution degree.

If you drink too much water and the urine is diluted, the plus signs will decrease; or if you drink too little water and the urine is highly concentrated, the plus signs will increase. In actual clinical work, it is often found that the patient's urine protein is qualitatively cloudy or cloudy, and the results may be different in the morning, afternoon, today, and tomorrow.

When looking at urine routine, you also need to look at the indicator of urine specific gravity, which can show whether the urine is diluted or concentrated, and then combined with plus and minus signs to judge.

There's another big catch: One plus has too much coverage.

Looking at the comparison table, 1+ corresponds to 0.3-1.5g. Looking up at the outcome of IgA nephropathy: 0.3g is in the safest group of renal function, and 1.5g is the group with the worst renal function.

Even if the urine retention concentration fully meets the standard, the plus and minus signs are difficult to serve as a reference for clinical diagnosis and treatment. Therefore, in the standard diagnosis and treatment process, nephrologists do not look at the plus and minus signs but look at the 24-hour urine protein quantification (and urine protein composition analysis).

Urinary protein is qualitative and cannot be used as a basis for diagnosis or treatment goals, but for physical examination or regular follow-up after the urinary protein is relieved and stable: negative (-) or weakly positive (+-) indicates that the condition is good; if there is 1 Plus sign (1+) or more plus signs, you need to check and quantify and treat according to the situation.

3 How much does the urinary albumin/creatinine ratio fall to the standard?

If these two ratios drop to the normal range or slightly increase, it means that the effect is good.

Although these two indicators are not as accurate as 24-hour urine protein, they are more accurate than the plus and minus signs of urine protein. The advantage is that only a single urination is required, and there is no need to keep urine for 24 hours, so the test is more convenient.

"KDIGO Nephropathy Clinical Practice Guidelines" recommends that when checking single urine, in addition to checking the qualitative urine protein, urine protein/creatinine ratio and urine microalbumin/creatinine ratio should be checked.

The ratio and quantitative matching of most patients are relatively good. For a small number of patients, if you find that your ratio and quantification are inconsistent with the above table, and there is a large gap, you may need to establish a dedicated control relationship for yourself, but it is recommended to check the 24-hour urine protein quantification.

for more information:ali.ma@wecistanche.com