Analysis of the causes of elevated CK-MB in heparin lithium blood collection tubes for children

1. Why is CK-MB higher in children than in adults?

In clinical biochemical testing, creatine kinase isoenzyme (CK-MB) is an important indicator for evaluating myocardial injury. Many inspectors have found that when using heparin lithium anticoagulant blood collection tubes to collect blood samples from children, the phenomenon of CK-MB detection values being significantly higher than that of adults. This phenomenon is not due to the higher incidence rate of myocardial injury in children, but is closely related to multiple factors in the use of blood collection vessels.

2. Core cause analysis

(1) The intrinsic effect of heparin lithium anticoagulant on CK-MB detection

Research has shown that there is a significant difference in CK-MB detection results between heparin lithium anticoagulant plasma and serum. The correlation between CK-MB values measured by heparin lithium anticoagulant plasma and serum test results is poor. The literature clearly states that items such as CK-MB should not be measured using heparin lithium anticoagulant plasma samples. This means that the heparin lithium blood collection tube itself will cause certain interference with CK-MB detection, which exists in different populations, but is more prominent in children.

(2) Insufficient filling of blood collection tubes - the primary factor for elevated CK-MB in children

There is a significant difference in blood collection between children and adults. Adult blood collection tubes are usually designed with a blood collection volume of 4ml, while pediatric blood collection volumes are generally 3ml. When the heparin lithium blood collection tube fails to reach the recommended filling volume, the vacuum pressure inside the tube becomes too high and the relative concentration of heparin increases, which can exacerbate red blood cell rupture (hemolysis) and release high concentrations of intracellular contents. Research has confirmed that insufficient filling of blood collection tubes can lead to significant changes in enzymatic indicators such as CK and GGT. Another study suggests that short drawn heparin lithium tubes may not be suitable for testing projects such as CK.

Children have small blood volume and thin blood vessels, making blood collection difficult and more prone to insufficient blood collection. Insufficient filling leads to high heparin concentration, while indicators such as CK-MB in plasma increase with increasing heparin concentration. This is precisely the pathophysiological mechanism by which elevated CK-MB levels in heparin lithium blood collection tubes are more common in children than in adults.

(3) Hemolysis is the direct driving force behind the pseudo elevation of CK-MB

Hemolysis is the direct cause of false elevation of CK-MB. Red blood cells contain high concentrations of enzymes such as creatine kinase (CK), which are released into the plasma after hemolysis, leading to artificially elevated detection values. Due to crying, lack of cooperation, and thin blood vessels during blood collection in children, the difficulty and operation time of puncture are high, and the high vacuum pressure caused by insufficient filling of blood collection vessels makes the risk of hemolysis in children's specimens much higher than that in adults. Research has shown that blood samples in heparin lithium tubes are more sensitive to hemolysis, and a hemolysis index exceeding 20 can interfere with CK-MB detection.

3. Response suggestions

(1) Select specialized blood collection tubes suitable for children's blood collection

It is recommended to use micro blood collection tubes specifically designed for children in clinical practice. These products have a reasonable blood collection volume design, accurate matching of anticoagulant content and blood collection volume, which can effectively avoid the problem of high heparin concentration caused by insufficient filling.

(2) Standardize blood collection procedures

Ensure that the blood collection tube is filled to the recommended blood volume; After blood collection, gently invert and mix 6-8 times to avoid severe shaking; Soothe the patient's emotions before blood collection, choose a suitable blood collection site, and try to be as precise as possible.

(3) Establish a reference system for children's plasma testing

Given the differences in CK-MB and other parameters between heparin lithium anticoagulant plasma and serum, it is recommended that clinical laboratories gradually establish a reference range for biochemical testing of pediatric plasma to avoid misjudging plasma test results based on serum standards.

Hubei Xindesheng Material Technology Co., Ltd. is a high-tech enterprise specializing in the field of IVD reagent raw materials. It was selected as a single champion enterprise in the manufacturing industry of Hubei Province in 2025. The company was founded in 2005 and specializes in the research, development, production, and sales of core products such as blood vessel additives, biological buffering agents, and chemiluminescence reagents.

In terms of heparin lithium products, the potency of Desheng heparin lithium is ≥ 150IU/mg. The company adheres to the product concept of "precision, stability, and innovation", and continues to provide high-quality anticoagulant raw materials such as heparin lithium for blood collection tube production enterprises. We are well aware that high-quality raw materials are the foundation of precise testing. Desheng will continue to use a rigorous scientific research attitude and strict quality control to help clinical testing become more accurate and reliable.