What should I do when the TT result becomes an asterisk and the retest is invalid?

Preface

The blood coagulation items are used as a routine checkup before admission and surgery.

Case history

Main medical history: The patient was an elderly male who had repeated heart palpitations and chest tightness for 10+ years before admission, aggravated with dizziness, and hematuria for 2+ days.

Past history: 51 years ago, the patient was hospitalized with “left empyema” due to “left pleurisy” in the First Affiliated Hospital of Chongqing Medical University, and underwent “closed thoracic drainage” and left lung abscess cavity compression.

Denies the history of infectious diseases such as hepatitis, tuberculosis, and typhoid fever

Physical examination: T: 36.

Randomly refers to blood sugar: 8.

ECG: Atrial fibrillation, ST segment changes

Head CT: bilateral lacunar foci in the basal ganglia

Chest radiograph: The left thorax was collapsed and shrunk, and the left lung was not displayed.

Laboratory examination

Liver function TG: 1.

Renal function T-Ca: 1.

The seven items of A Gong were normal

Myocardial injury marker BNP: 0.

Blood routine Lym%: 9.

Six coagulation PT: 12.

At this time, when I saw the TT result was an asterisk, I was confused.

So I followed the procedure for review of abnormal results in the department and began to reverse the calculation
.
The instrument used in the department uses the coagulation method to detect TT, the instrument is operating normally, and the results of the specimens before and after are normal
.
The quality control was under control on that day, and the reagents were not changed before and after the specimens.
All coagulation specimens were tested by me.
The patient’s specimens were free of lipids, hemolysis, jaundice, and clots
.
Human factors, equipment, reagents and other factors have been eliminated
.

So I followed the manual method in the TT manual, and the results of the three times were all greater than 300S.
The upper limit of the TT of our instrument is 160S.
No wonder there will be asterisks
.

Therefore, the main reason is still concentrated on the patient itself.
Could it be that the production of coagulation factors is affected? But liver function and other blood coagulation results are normal, and there are anticoagulants similar to lupus in the body?

However, after asking the clinician, there was no clear result, so he consulted with the engineer.
The engineer said that in this case, anticoagulants, such as heparin, warfarin, aspirin, etc.
, have the greatest impact, but the patients have not taken the above drugs.
The engineer mentioned that there are still New oral anticoagulant drugs, such as apixaban, rivaroxaban, dabigatran, etc.
At this time, when I saw the word "dabigatran", I thought that the case stated that the patient had done it 5 years ago I have been taking dabigatran after carotid artery stent implantation, and I got a definite answer after asking the clinician.
The reason was found.
The engineer suggested that my TT result was greater than the upper limit of detection, because even if the blood was drawn again, it would not make much sense.
After communicating with clinicians, this result was also issued smoothly, but the reason has not been completely resolved.
Why does dabigatran affect TT? How does it affect it?

case analysis

Before understanding dabigatran, let's review the meaning of TT
.

TT: Thrombin time measurement refers to the time required for plasma fibrinogen to be converted into fibrin after adding "standardized" thrombin to plasma
.
This shows that if you want it to not coagulate, you have to affect the thrombin in it
.

Dabigatran is a direct thrombin inhibitor, which is quite different from warfarin by inhibiting the activation of vitamin K-dependent coagulation factors.
It directly inhibits a single coagulation factor in the coagulation waterfall, such as factor II.
It binds to the fibrin-specific binding site of thrombin to prevent fibrinogen from cleavage into fibrin, thereby blocking the final step of the coagulation waterfall network and thrombosis
.
Dabigatran can also dissociate from the fibrin-thrombin conjugate and exert a reversible anticoagulant effect
.
It has a predictable and stable anticoagulant effect, with fewer drug interactions and no drug-food interactions
.

Therefore, we can know that dabigatran can indeed affect the results of TT detection.
Studies have shown that TT is highly sensitive to dabigatran in the blood.
Dabigatran at lower than the therapeutic concentration can also prolong TT, such as 60ng/ The blood drug concentration in mL often prolongs the patient's TT by >300s, which also confirms that the previous manual method results >300s.
The drug can take effect about 1 hour after oral administration, and its drug concentration reaches its peak in about 2 hours.
The half-life is about 12 hours, and about 80% is excreted in the original form through the kidneys, and TT is too sensitive to dabigatran, and is generally not used as an indicator of coagulation function, but it can be used as a qualitative indicator to determine whether there is still in the body Drug residues
.

In the end, the cause of the TT result star was found, and I will continue to pay attention to the impact of similar drugs on the coagulation results in my work in the future
.

Summarize

As an inspection worker, meticulousness is the basic requirement.
When we see abnormal results, we should learn to reverse it.
We can look for the cause from factors such as personnel, machinery, reagents, methods, and environment, rather than just before understanding the reason.
Send out the report, causing clinical misunderstanding
.
In addition to dabigatran which acts on factor Ⅱ, new anticoagulants also include rivaroxaban, apixaban and edoxaban which act on factor X.
In our work, we should draw inferences from one another, not just Limited to one place, only in this way can we accumulate more experience
.