Urine hCG positive, serum hCG negative, what causes it?

Preface

Human chorionic gonadotropin (HCG) is a glycoprotein secreted by the trophoblast cells of the placenta and is composed of
glycoproteins of α and β dimers.
The glycoprotein hormone with a molecular weight of 36700, the α subunit is basically similar to the FSH (follicle-stimulating hormone), LH (luteinizing hormone) and TSH (thyroid-stimulating hormone) secreted by the pituitary gland, so it can cross-react with each other, while the structure of the β subunit is not similar
.
When the pregnancy is 1~2.
5 weeks, the level of hCG in serum and urine can increase rapidly, and the serum HCG concentration peaks in the 8th-10th week, lasts for about 10 days and then drops rapidly, and the serum concentration in the second and third trimesters of pregnancy is only 10% of the peak and lasts until delivery
.

Case history

The patient, female, 28 years old, felt unprovoked lower abdominal pain 10 hours ago, persistent, and not severe
.
In order to seek medical treatment, I came to our hospital
.
Outpatient "abdominal pain" admitted to our hospital, patients reported regular menstruation, cycle 28-32 days, now feel frequent urination, urgency, difficulty urinating, no vaginal bleeding, no dizziness, fatigue, chest tightness, shortness of breath and other discomfort, no fever, cough, sputum and other symptoms
.

Laboratory tests: blood analysis five classifications, urinalysis, urine pregnancy test, serum hCG and other test items
.

Laboratory results show:

WBC: 17.
19X10*9/L, NE: 15.
93X10*9/L, PCT: 2.
891ng/ml, FIB: 1.
50g/L, HCG: <0.
100IU/L, urine pregnancy test: positive (+)[1], other results were not significantly abnormal.

Case study

The patient is a woman of childbearing age, the following abdominal pain is admitted to the hospital, the clinician immediately prescribes the examination items, and the telephone informed our department that the patient requested to be urgent, and after receiving the specimen, the personnel of each position immediately began the experiment, the test results showed: urine pregnancy test (+), after confirming that the report was correct, is it an ectopic pregnancy? However, based on this test item alone, it is difficult to conclude, and then the serum hCG test results showed that the hCG < 0.
100IU/L, why?

Women of childbearing age because the fertilized egg moved to the uterine cavity after implantation, the formation of embryos, in the process of development and growth into the fetus, placental syncytiotrophoblast cells produce a large amount of HCG, which can be excreted into the urine through the blood circulation of pregnant women, and this result is just the opposite, so the urine sample is used as a blood sample for testing, the test results show: HCG concentration: 48.
20IU/L, urine does contain low concentrations of HCG, why can it not be detected in serum
.

The results of the urine pregnancy test and serum hCG were the same as the initial test results, and then the clinician was immediately contacted to inform the test results, and the test results were confirmed, but the cause of this abnormal result is still unclear and needs to be further explored
.

Cause analysis:

1.
Verify that the instrument performance, indoor quality control, and specimen status on the day are correct
.

2.
Check that the HCG test strip meets the placement requirements within the validity period and the storage place, and there is no abnormality
in the test results of other patients on the same day.

3.
Serum HCG is negative, and the urine pregnancy test is positive, the problem of false positives should first be considered, which may be related to the concentration of urine, and the patient has defecated 2 hours ago, which can basically exclude false positives
caused by urine concentration.

Laboratory tests can be basically confirmed, so what is the reason for this abnormal test result, because of other diseases? With doubts to check the data, the data indicates that the diseases with this test result are: ovarian cyst, uterine chorionic epithelial cell carcinoma [1], so the call told the clinician that it is recommended to test female tumor markers and other items
.

After asking the ultrasound department, the patient's ultrasound results: uterus: smooth margin, posterior position
.
The size of the uterine body is about 59 mmx37 mmx37 mm, the echo of the muscle wall is uniform, and the inner membrane is about 7 mm thick and centered
.
The cervix is about 18 mm
thick.
Attachments: Cystic mass of about 47x32mm in size on the right side, visible in the septum, CDFI: blood flow signal visible on the septum, and cystic mass
of about 33x26mm in size in the left adnexal area.
Uterorectal fossa probe and liquid dark area 10 mm
.

The patient's clinical manifestations were obvious, combined with ultrasound examination and laboratory test results, the operation was performed on the second day of admission: laparoscopic left ovarian endometriosis cyst excision + bilateral salpingostomy + pelvic adhesiolysis, which was successfully completed
.
Clinical diagnosis is initially diagnosed by admission: 1.
Ectopic pregnancy? 2.
Bilateral ovarian tumor and other diagnosis, modified to: 1.
Right fallopian tube abscess 2.
Left salpingosalpinx 3.
Left ovarian endometriosis cyst and other accurate diagnosis
.
The patient's symptoms are eliminated, his mental outlook is good, he is discharged from the hospital, and he is followed up
regularly.

Case summary

In the daily examination work, urine pregnancy test detection is fast and time-consuming, and is favored by patients
.
However, women of childbearing age can not directly indicate pregnancy when urine hCG positive, because urine hCG is easily disturbed by other factors, more false positives, should be combined with serum hCG test results specific analysis, can not blindly issue a report, can not mislead the doctor's diagnosis and treatment, this case The reason for this result is that the patient has right tubal abscess, left salpingosalpingoscopis and left ovarian endometriosis cyst [2] and other diseases
.
Therefore, the examiner should communicate with the clinical in a timely manner, combine other examinations, and comprehensively analyze to truly serve the clinic and the patient
.

References

[1] JIANG Donghe.
Discussion on the experience of false positive and false negative urinary hCG in diagnosis and treatment.
Clinical Highlights,2012.
12.
258 1004-7484(2012)-5085-01.

[2] Zhao Q，YangJ，CaoD，etal.
Tailored therapy and long-term surveillance of malignant germcell tumors in the female genital system ： 10-yearexperience[J/OL].
JGynecolOncol ，2016，27：e26.