The interference of chylosing blood on blood routine is often overlooked by us

With the improvement of modern living standards, chylosing blood is very common in clinical practice. So what is chylosing blood? Simply put, chylosing blood is "blood with floating oil" or "lipidemia". The plasma is milky white or turbid, like cream, and is more common in people with hyperlipidemia. Chylosing blood samples usually interfere with the detection results of hemoglobin in routine blood tests, causing the hemoglobin value to be falsely high. This interference is often ignored by us, especially when the venous blood is not centrifuged, chylosing blood samples are difficult to identify quickly. When the average hemoglobin concentration in the test report of a patient with hyperlipidemia is increased, the interference of chylosing blood on hemoglobin may be ignored. This article shares a case in which chylosing blood interfered with the results of a routine blood test.

On November 10, 2023, when reviewing the samples, it was found that the red blood cells (RBC) of one sample was 4.63×1012/L, the hemoglobin (HGB) was 162 g/L, and the mean hemoglobin concentration (MCHC) was 409 g/L. The results of the first test are shown in Figure 1.

Figure 1

The test results showed that the MCHC was 409g/L, which was higher than the upper limit of the normal reference value (360 g/L). There are two common clinical causes of elevated MCHC: one is red blood cell agglutination, and the other is chylomicronized blood, jaundice, or high white blood cell specimens. If it is caused by red blood cell agglutination, the red blood cell count and hematocrit (HCT) will be very low, and red blood cells will be aggregated under the microscope. The patient's specimen was observed to have no aggregation of red blood cells under the slide microscope. At the same time, the patient's biochemical results were checked and it was found that his triglyceride was 24.42mmol/L and total cholesterol was 10.34mmol/L, both of which were far higher than the upper limit of normal values. Therefore, it is speculated that the patient's MCHC elevation was caused by chylomicronized blood. The specimen was then centrifuged, and the plasma after centrifugation is shown in Figure 2.

Figure 2

Looking back, why did the abnormal increase of MCHC attract our attention? Because it serves as a warning. MCHC=HGB/HCT. An increase in MCHC means that the numerator HGB is falsely high or the denominator HCT is falsely low. Regardless of whether HGB is falsely high or HCT is falsely low, the results are disturbing and incorrect for patients, which will have a great impact on the clinical diagnosis and evaluation of patients' diseases. Therefore, the abnormal increase of MCHC needs to attract our attention. We have mentioned above that when red blood cell agglutination occurs, HCT will be falsely reduced, but this patient did not have red blood cell agglutination. Therefore, the reason for the increase in MCHC in this patient is due to falsely high HGB.

The patient had chylomicrons, which means that chylomicrons caused a falsely high hemoglobin measurement, which in turn caused an abnormally high MCHC value. The blood test analyzer detects hemoglobin based on the colorimetric method, that is, adding hemolysin to destroy the red blood cells in the sample, releasing hemoglobin, and then the instrument performs colorimetric analysis on the solution. The chylomicrons in chylomicrons affect the colorimetric analysis, which in turn affects the HGB result, causing a falsely high result, which in turn causes an abnormally high MCHC value.

Well then, how should we correct this patient's chylosing blood that causes falsely high HGB and elevated MCHC?

Generally we use the formula correction method to make corrections.

Calculation formula: HGB corrected value = HGB before correction - (HGB chylomas - HGB chylomas × HCT before correction)

MCHC corrected value = HGB corrected value / HCT before correction

The above methods can correct the results of HGB to a certain extent, reduce the impact of chylomicronized blood on HGB detection, and obtain the true value of HGB.

After the patient was corrected using the formula correction method, HGB dropped from 162 g/L to 134 g/L, and MCHC dropped from 409 g/L to 338 g/L, both falling within the normal reference range. Finally, the patient was given a relatively accurate test report, see Figure 3.

Figure 3

Since the routine blood test uses whole blood for testing and the samples are mixed, it is difficult to detect chylomicron with the naked eye. Therefore, we need to pay special attention to the MCHC value when reviewing the results, and promptly detect and correct chylomicron when it occurs to avoid the invisible interference of chylomicron on the routine blood test results, thereby ensuring the accuracy of the results.

About the Author

Lu Yuexian

Tangshan Workers' Hospital Laboratory Department

Chief Inspector