Application in obstetrics and gynecology
In routine clinical practice, screening of thyroid function plays a paramount role in maintaining the health of the mother and fetus. Determination of anti-thyroperoxidase antibody levels is prescribed to strictly defined groups of women:
- For patients who are planning conception, i.e., at the pre-gravid stage.
- For pregnant patients. In this case, the laboratory test is performed once, directly during the first visit to a specialist.
The evaluation of obtained anti-TPO results is always carried out in inseparable connection with thyroid-stimulating hormone (TSH) levels. There are clear indications in which a patient must be referred for a consultation with an endocrinologist to decide on the administration of specific therapy for hypothyroidism (this algorithm has the highest recommendation validity level A and evidence reliability level 2):
- TSH level exceeds 2.5 IU/mL with the simultaneous confirmed presence of anti-TPO (positive result).
- TSH level exceeds 4.0 IU/mL. In this clinical situation, a consultation with a subspecialist is required regardless of whether anti-thyroperoxidase antibodies are detected or not.
Preparation for antiviral and immunostimulatory therapy
The functional status of the thyroid gland must be thoroughly checked in patients for whom the administration of immunostimulants or major etiotropic therapy is planned. According to current clinical guidelines (Level of Recommendation Validity C, Level of Evidence Reliability 5), all patients receiving immunostimulatory drugs require mandatory laboratory monitoring.
Special attention in clinical practice is paid to patients with diagnosed viral hepatitis D (HDV) who are scheduled for interferon treatment. Strictly prior to the initiation of such therapy, the following are performed:
- Quantitative PCR: determination of hepatitis D virus RNA (HDV RNA) if technically feasible.
- Thyroid function assessment to rule out occult underlying pathology. For this purpose, anti-TPO, thyroid-stimulating hormone (TSH), and free thyroxine (free T4) serum levels are examined.
Additionally, before starting immunostimulatory treatment, anti-thyroglobulin antibody (anti-Tg) levels may be tested. If deviations in TSH levels are detected during treatment (at the laboratory monitoring stage), the patient is immediately scheduled for an advanced workup to precisely clarify the etiology of the changes that have occurred.
The role of anti-TPO in differential diagnosis
The anti-thyroperoxidase antibody test is included in the expanded list of laboratory tests intended for differential diagnosis and ruling out various comorbid conditions as well as similar pathologies. During a comprehensive examination, in addition to assessing thyroid function (TSH, free T4, anti-TPO, thyroglobulin), the attending physician prescribes a number of related tests.
The standard differential diagnostic profile includes the following important areas:
- Blood biochemistry and hemostasis: mandatory assessment of total calcium and fibrinogen levels.
- Urinalysis: general (clinical) urinalysis with mandatory microscopic examination of urine sediment.
- Infectious serology: detailed search for markers of viral infections. This block includes the detection of classes M and G antibodies (IgM, IgG) to human immunodeficiency viruses (HIV-1 and HIV-2), antibodies to hepatitis C virus, as well as screening for hepatitis B (surface antigen HBsAg, antibodies to HBsAg and core antigen HBcAg).
- Rheumatological and autoimmune profile: determination of antinuclear antibodies and anti-DNA antibodies.
To remember the indications for an endocrinologist consultation during pregnancy, use the rule "Two and a half with a plus, four with any": if TSH > 2.5 IU/mL, a "plus" (presence of anti-TPO) is needed, and if TSH > 4.0 IU/mL, the anti-TPO status no longer matters.
Class and exam questions
Is it necessary to take the anti-TPO test multiple times throughout pregnancy?
No, according to modern clinical guidelines, this laboratory test is performed strictly once for pregnant patients during their first visit to the physician.
Which thyroid tests are needed before starting interferon therapy?
Strictly prior to initiating etiotropic antiviral treatment, it is necessary to determine the levels of anti-TPO, thyroid-stimulating hormone (TSH), and free thyroxine (free T4) in the patient's blood serum.
What to do if TSH levels change during treatment with immunostimulants?
If any deviations in thyroid-stimulating hormone levels are detected during laboratory monitoring, it is necessary to promptly conduct a comprehensive additional examination of the patient to clarify the etiology of the pathological process.
Is a single anti-TPO value sufficient to assess thyroid function?
No, anti-thyroperoxidase antibodies are always evaluated in an inseparable complex with thyroid-stimulating hormone (TSH), and in some cases, with free thyroxine (free T4) and anti-thyroglobulin antibodies (anti-Tg).
What else to study on this topic
- Interpretation of viral hepatitis B markers: surface antigen HBsAg, antibodies to HBsAg and HBcAg.
- The role of quantitative PCR (determination of HDV RNA) in preparation for viral hepatitis D treatment.
- Serological diagnostics of rheumatological diseases: antinuclear antibodies and anti-DNA antibodies.
- Anti-thyroglobulin antibodies (anti-Tg) as an additional marker when prescribing immunostimulants.
- Clinical significance of microscopic examination of sediment in general urinalysis.
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