Don't panic when you see an "arrow" on the test report

This is the 4490th article of Da Yi Xiao Hu

Faced with the obscure academic terms and dense numbers on the test report, many friends will be confused and often take a convenient approach, directly looking for "arrows": "values ​​higher than normal" are generally indicated by "↑", and "values ​​lower than normal" are indicated by "↓". It can be said that this is a rough and effective way to roughly understand whether your test items are within the normal reference value range through the "arrows", reminding yourself to pay close attention to your physical health. However, we don't have to be anxious when we see the indicators with floating up and down arrows. Going to the doctor to see the results has a sense of excitement and tension of "opening a blind box".

Here, I would like to introduce three values ​​to you, "reference value", "medically determined level" and "critical value", to help you explain: why sometimes we feel anxious and go to the doctor with test reports showing "up and down" arrows, but after looking at the doctor, the doctor just tells us calmly how to improve our lifestyle.

What we see on the test report is the reference value, which is a statistical range of values. It refers to the measured values ​​obtained from the selected "normal" reference population, and the indicator value range of the vast majority of "normal people" (generally 95% of people). The measured values ​​of indicators vary not only from person to person, but also change with changes in specific internal and external environment and physiological conditions, so they will fluctuate within a range. It can also be understood that the obtained value range only covers 95% of people, and even if the remaining 5% of people are not sick, their measured values ​​may fall outside the reference value range. (Not accurate, but it is also acceptable to understand it this way)

Abnormal values ​​that are not much beyond the reference value limit can be treated differently according to the patient's clinical manifestations. Treatment measures can be taken or observation can be carried out. However, if it exceeds the limit of the medical decision level, treatment measures must be taken in time. The diagnostic indicators of some diseases must rely on the medical decision level value to be judged, and it is difficult to judge around the reference value range. After we get a measured value that exceeds the reference value range, whether to take medical intervention measures, doctors also have a set of indicators based on a large number of clinical studies, namely the medical decision level, to guide practical operations. By whether the measured value is higher or lower than these limits, the disease can be excluded or confirmed, the disease can be graded or classified, the prognosis can be estimated, and decisions can be made on what treatment method to take and what treatment measures to take.

The reference range of alanine aminotransferase (ALT) is 5-40IU/L, which means that 95% of healthy people's ALT values ​​are within this range, but there are three medical decision levels. The first decision level is 300IU/L. Values ​​above this level indicate extreme liver cell damage. The second decision level is 60IU/L. When the ALT value is between 40-60IU/L, it is not certain whether the increase in ALT is a pathological change. Many obese people who are not very healthy have ALT values ​​that fluctuate within this range. Only when the ALT value is greater than 60IU/L can it be clearly diagnosed as liver cell damage, so it is a confirmation value. The third medical decision level is 20IU/L, which is an exclusion value, that is, many diseases related to ALT elevation can be excluded if the value is lower than this value.

The reference range for alpha-fetoprotein (AFP) testing is AFP < 25µg/L, while AFP > 25µg/L may indicate diseases such as hepatitis and cirrhosis. AFP > 400µg/L is the threshold for diagnosing primary liver cancer, which is 16 times the upper limit of the reference range. Therefore, for the purpose of diagnosing liver cancer, the reference range of AFP is meaningless.

The medical decision level is the data that clinicians should master and use when diagnosing and treating diseases. It is not a reference value for ordinary patients. The medical decision level comes from a large amount of medical practice, experience and scientific research. It is the basic knowledge that clinicians and clinical laboratory staff should master.

Finally, let's talk about "critical values", also known as emergency values ​​or warning values, which indicate life-threatening test results and are a threshold in the medical decision level. When such test results appear, it means that the patient may be on the verge of life-threatening conditions. After receiving such test information, clinicians should promptly provide patients with effective intervention measures or treatments, otherwise they may lose the best chance of rescue, leading to serious consequences. Therefore, this type of experimental data is called a "critical value."

Taking diabetes as an example, the reference range for healthy people is usually 3.9-6.1mmol/L. When fasting blood sugar is ≥7.0mmol/L, or any blood sugar is ≥11.1mmol/L, the diagnosis of diabetes should be considered. However, when blood sugar is ≥22.2mmol/L, diabetic coma will occur, and rescue must be carried out at this time; similarly, when blood sugar is ≤2.2 mmol/L, hypoglycemia shock will occur, and rescue must also be carried out immediately. Therefore, 22.2mmol/L and 2.2mmol/L are critical values ​​for blood sugar measurement, and 7.0mmol/L or 11.1mmol/L are the thresholds for diagnosing diabetes. At this time, the clinic must consider corresponding treatment measures, but it is not a critical value yet.

Therefore, when we see the "arrow" on the test report, don't panic or rush to Baidu. The abnormality of one or two indicators and the clear diagnosis of the disease often require comprehensive analysis by professionals or even multidisciplinary professionals to draw a conclusion.

Author: Hematology Hospital, Chinese Academy of Medical Sciences

Wang Hailong