Laboratory diagnostics in gynecology

Evaluation of ovulation via basal body temperature

The basal (rectal) temperature chart provides an indirect assessment of a woman's hormonal background throughout a 28-day cycle.

• Biphasic curve: a sign of a normal ovulatory cycle. In the follicular phase, the temperature remains low (36.4–36.8 °C) under the influence of estrogens. After ovulation, the corpus luteum is formed (corpus luteum). It secretes progesterone, which acts on the thermoregulatory center, raising the temperature above 37.0 °C (luteal phase).
• Monophasic curve: a sign of an anovulatory cycle. The corpus luteum does not form, progesterone is not released, and therefore there is no sustained temperature rise in the second half of the cycle. The cycle occurs against the background of hyperestrogenism.

Microflora analysis and infection diagnostics

To determine the composition of the vaginal flora, a smear for the degree of cleanliness is used. The material is collected with a Volkmann spoon (without prior douching), applied to two glass slides, and stained with methylene blue and Gram stain.

Four degrees of vaginal cleanliness are distinguished:

1. Grade I: single leukocytes, flora consists exclusively of lactobacilli.
2. Grade II: 10–15 leukocytes per high-power field, rod flora, and single cocci.
3. Grade III: 30–40 leukocytes, few lactobacilli, cocci predominate.
4. Grade IV: high number of leukocytes, lactobacilli are absent, various microorganisms are detected (including gonococci and trichomonads).

For accurate identification of infectious agents, the following are used:

• PCR (molecular biological method) — detection of specific DNA segments of the microorganism.
• ELISA and direct immunofluorescence (serological tests) — detection of antibodies or antigens based on the "antigen-antibody" reaction.
• Culture method — optimal for intracellular parasites (e.g., chlamydia).
• Bacteriological culture — growing colonies on nutrient media followed by the assessment of their antibiotic susceptibility.

Cytological examination and biopsy

Cytological diagnostics — the main screening tool for detecting oncological diseases. The material consists of cervical smears, uterine cavity aspirates, or punch biopsies. The method evaluates cell morphology and their quantitative ratio.

Cervical smear results are most often classified according to the Papanicolaou system (Pap test):

• Class I: normal cytological picture.
• Class II: inflammatory or reactive epithelial changes.
• Class III: suspicion of dysplasia (atypia of individual cells).
• Class IV: suspicion of cancer (isolated malignant cells).
• Class V: cervical cancer (clusters of malignant cells).

When pathology is detected, a biopsy is indicated — the intravital sampling of a small volume of tissue. It can be excisional (excising a piece), punch, or targeted (performed under visual control of a colposcope).

Hormonal profile and functional tests

Laboratory evaluation of endocrine function includes blood tests for protein hormones (LH, FSH, prolactin) and steroid hormones (estradiol, progesterone, testosterone), as well as urine tests for metabolites (e.g., 17-ketosteroids).

Since a single hormone determination has low diagnostic value, functional tests are used to check the reserve capacities of the reproductive system:

• Low-dose dexamethasone suppression test: helps find the source of hyperandrogenism in virilization. Dexamethasone suppresses ACTH production by the pituitary gland. If the androgen level drops by more than 50–75% after administration, the hyperandrogenism is of adrenal origin. If it decreases by less than 25–30%, it is of ovarian origin.
• Clomiphene test: evaluates the hypothalamic-pituitary system in chronic anovulation. A positive response (increase in gonadotropins and estradiol) indicates preserved system function.
• Estrogen and progestin test: used to rule out the uterine form of amenorrhea. The onset of a menstrual-like reaction indicates a deficiency of endogenous estrogens, while its absence indicates organic endometrial damage.

Colposcopy as a stage of material sampling

Although colposcopy belongs to endoscopic methods, it is inextricably linked with laboratory diagnostics, as it allows for an accurate targeted biopsy.

• Extended colposcopy: the cervix is treated with a 3% acetic acid solution. Normal vessels spasm and disappear, while pathologically dilated ones (lacking muscular elements) remain gaping. The epithelium turns white due to protein coagulation.
• Schiller's test: treatment with a 3% Lugol's solution. Healthy squamous epithelium stains dark brown with iodine. Atrophic or pathologically altered cells do not stain, which guides the physician to the exact site for biopsy sampling.

Class and exam questions

What else to study on this topic

• High-dose dexamethasone suppression test and diagnosis of virilizing tumors
• Dynamics of hCG levels in a normally developing intrauterine pregnancy
• Indications and types of diagnostic hysteroscopy
• Methodology of the estrogen and progestin test
• Features of the vascular pattern in extended colposcopy

Other topics in the "Gynecology" section

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