Xie Shasha The kidney is online
24-hour urine protein quantitative is the gold standard for evaluating the severity of urine protein, and it is affordable and widely used in clinical practice.
But as the saying goes, "No one is perfect", 24-hour urine also has its disadvantage, that is, it is too troublesome to keep ! Some people who are not sure about the method of retaining urine are prone to keeping mistakes, which affects the results.
So, clinically, we have figured out a test method that can replace 24-hour urine, which can not only quantitatively analyze the severity of urine protein, but also facilitate patients' operation: ACR (urinary albumin creatinine ratio) and PCR (urinary protein creatinine ratio), and leave a single urine. It is not easy to understand these two tests, and some issues with are also controversial in medicine.
We sorted out the common doubts that everyone encountered as follows. The knowledge points are difficult. If you can’t understand them, please read them several times.
1. What kind of check are ACR and PCR?
Please note that although the names look very similar, they are not a check, there is a difference!
ACR (albumin-to-creatinine ratio) is the abbreviation of " urine albumin creatinine ratio "; (and urine microalbumin creatinine ratio, which means the same)
PCR (protein-to-creatinine ratio) is the abbreviation of " urine creatinine ratio ".
ACR checked the severity of albumin in the patient, and PCR checked the severity of total protein in the patient. (The total protein is also measured in 24-hour urine protein quantification)
ACR and PCR test sheet▽
2. Why can ACR and PCR replace 24-hour urine protein quantification
Because the research found that the values of ACR and PCR can be inferred that 24-hour urine protein quantification can be estimated.
You can see the following figure. The PCR value (red dot part) basically coincides with the 24-hour urine protein quantification (line part). The red dot sways near the straight line, indicating that the values of the two are basically matched.
3. How to estimate the 24-hour urine protein quantification through the values of ACR and PCR?
The following table shows the general correspondence between ACR and PCR:
The reason why it is said to be " general correspondence" is added to the word "general" because the values of ACR and PCR in many patients have a very good match with 24-hour urine protein.
However, not every kidney friend meets the corresponding relationship of this table, and it is also possible that there is no or mismatch.
4. Use the test sheet examples of 2 patients to illustrate
to see the test sheet of this patient. The ACR is 361mg/g and PCR is 684mg/g. Then the 24-hour urine protein quantification corresponding to this patient should be greater than 500mg, about 684mg.
Let’s look at this patient again. The ACR is 237mg/g and the PCR is 421mg/g. The 24-hour urine protein quantification corresponding to this patient should be between 150-500mg, about 421mg.
5. Where to check? How to keep urine?
Not all nephrology departments have carried out these two examinations. Some can check, some cannot check, and some hospitals have only carried out one of them. If you want to check, you can ask your doctor.
ACR and PCR can be checked at the same time with one tube of urine, and you can keep it once.
The specific method of retaining urine is similar to the routine of retaining urine:
is usually the best requirement for morning urine (the first time I wake up in the morning) , because studies have found that the correspondence between morning urine and 24 hours is the best. If you really can't hold back your morning urine, you can also use the second random urine after morning urine. avoids the impact of exercise .
6.Unit conversion
Unit conversion: mg/g converts mg/mmol, need to divide by 8.8
such as ACR30mg/g, equivalent to 3.4mg/mmol
mg/g converted to g/g, need to divide by 1000
such as PCR3000mg/g, equivalent to 3g/g
7. Why is ACR and PCR controversial?
Speaking of this, some people may be confused: "Since it is so convenient to check once, and it is not necessary to collect 24-hour urine urine, why don't the hospital use them instead of 24-hour urine protein quantification?"
This is because ACR and PCR are still controversial. The focus of the controversy is that they may miscalculate the 24-hour urine protein quantification in some patients.
below describes the reasons for the controversy. You may not understand it, it doesn’t matter if you don’t understand it. Just jump to question 8 and teach you some practical solutions.
1) is affected by urine creatinine excretion
When we use ACR and PCR to speculate that 24-hour urine protein quantification is assumed that each person's urine creatinine excretion is 1000mg per day. But in fact, if some patients are stronger than ordinary people, eat more meat, and have more urine creatinine excretion, and more than 1000mg a day, the values of ACR and PCR will underestimate the 24-hour urine protein quantification. The actual 24-hour urine protein quantification should be higher than the estimated values of ACR and PCR.
and vice versa. Some patients are thinner than ordinary people, with less urinary creatinine excretion, and the values of ACR and PCR will overestimate the 24-hour urine protein quantification.
2) The urine protein itself fluctuates
The urine protein excretion in the afternoon (random urine during the day) can be 50% higher than the excretion in sleep time (morning urine).
Assuming that a patient with nephropathy has a 24-hour urine protein quantification that was originally stable at 2000 mg.
The first time he checked for PCR, he used morning urine. PCR 1600mg/g was found to be found for morning urine. The second time he checked, the afternoon urine protein was used (because of activities, etc.) PCR 2400mg/g. The actual urine protein in this patient was stable at 2g and did not change. However, if we look at PCR alone, the result of the second time was more serious than the first time, and the urine protein was actually not worsened.
8.Teach you some practical methods to eliminate errors
When checking ACR and PCR for the first few times, we also checked 24 hours of urine and compared to correspond to the matching degree.
matches well. In the future, they can be used instead of 24-hour urine protein quantitatively to monitor changes in your urine protein, which can facilitate future follow-up.
In addition, you can check whether there is a fixed coefficient according to the corresponding rules of PCR and 24-hour urine protein quantification. For example, it may be found that every time your PCR value is multiplied by a number, you can get a 24-hour urine protein quantification.
For patients with poor matching, it is recommended to check 24-hour urine protein quantification.
9. What should I do if the difference between ACR and PCR is large?
Because we patients with kidney disease, most of the urine protein is mainly composed of albumin, and the matching degree of ACR and PCR is relatively good.
However, there are patients with PCR and ACR that do not seem to match:
1) ACR exceeds the standard, while PCR is normal
This situation is seen in patients with very little proteinuria. This is also the advantage of
ACR. Some patients with early-stage high-risk kidney disease (such as diabetes, hypertension, gout, people with a family history of kidney disease, etc.) need to undergo kidney disease screening. ACR can detect extremely mild urine protein abnormalities at the earliest, which is more sensitive than other urine tests.
If you are a kidney friend, it means that your urine protein has been well controlled, and only a very small amount of urine protein is abnormal.
2) ACR is close to normal, but PCR is very high
means that the protein in urine is not mainly albumin, but other protein components cause urine protein to exceed the standard.
For example, it is common for patients with renal tubular interstitial injury as the main , and the urine protein of these patients is mainly β2 microglobulin, retinol-binding protein, etc.; when the ACR divided by the PCR value is less than 0.4, it can be inferred that this patient is most likely a patient with tumour interstitial injury as the main tumour interstitial injury.
and rare cases, tumor patients, immunoglobulin light chains for multiple myeloma, and lysozymes in leukemia patients.
10.ACR and PCR control targets?
Our kidney friends control ACR to within 300mg/g and PCR to within 500mg/g.
