Type of test Blood; urine

Normal findings

 • Negative: < 5 IU/L

• Indeterminate: 5-25 IU/L

• Positive: > 25 IU/L

• Males and nonpregnant females: < 2 IU/L

Test explanation and related physiology

All pregnancy tests are based on the detection of human chorionic gonadotropin (hCG). hCG appears in the blood and urine of pregnant women within days after conception.

hCG is made up of alpha and beta subunits. The beta subunit is specific for hCG.

Very small levels of hCG can be detected and pregnancy can be determined 3 to 7 days after conception. There is no cross over reactivity with other non-hCG glycoprotein hormones. The diagnostic cutoff for pregnancy is greater than 25 IU/L. Values between 5 and 25 IU/L are indeterminate for pregnancy. Results can be confirmed with a repeat test in 72 hours. Values in pregnancy should double every 3 days for the first 6 weeks. When an embryo is first large enough to be visible on transvaginal ultrasonography , the patient generally will have hCG concentrations between 1000 and 2000 IU/L. If the hCG value is high and gestational contents are not visible in the uterus, an ectopic pregnancy is suggested.

There are qualitative serum and urine hCG assays and quantitative serum hCG assays (Table 1). In the home setting, the urine is applied to a testing apparatus, and the color change is compared with a standard. If the color matches that standard, pregnancy is present. Other test kits use the development of a line or plus symbol that may appear indicating pregnancy. These tests take only a few minutes to perform and to obtain results. They are best if performed a few days after a missed menses. However, results can be positive on the day of an expected menses.

Table1. Recommended uses for hCG testing

Concentrations of hCG level off around week 20, significantly above prepregnancy levels. After delivery, miscarriage, or pregnancy termination, hCG falls until prepregnancy levels are reached.

Normally, hCG is not present in nonpregnant women. In a very small number of women (< 5%), hCG exists in minute levels. The presence of hCG does not necessarily indicate a normal pregnancy. Ectopic pregnancy, hydatidiform mole of the uterus, recent abortion, and choriocarcinoma can all produce hCG. However, hCG levels in ectopic pregnancy typically fail to double appropriately, and decreased levels eventually result relative to the values expected in normal intrauterine pregnancies of simi lar gestational age. hCG may be secreted by seminomatous and nonseminomatous testicular tumors, ovarian germ cell tumors, and benign or malignant nontesticular teratomas . Serial measurement of hCG after treatment is used to monitor therapeutic response in these tumors and will detect persistent or recurrent neoplastic disease.

 Interfering factors

• Tests performed too early in the pregnancy, before a significant hCG level exists, may cause false-negative results.

 • Hematuria and proteinuria may cause false-positive results.

 • Hemolysis of blood may interfere with test results.

• Urine pregnancy tests can vary according to the dilution of the urine. hCG levels may not be detectable in dilute urine but may be detectable in concentrated urine.

* Drugs that may cause false-negative urine results include diuretics (by causing diluted urine) and promethazine.

* Drugs that may cause false-positive results include anticonvulsants, antiparkinsonian drugs, hypnotics, and tranquilizers (especially promazine and its derivatives).

 Procedure and patient care

 Before

* Explain the procedure to the patient.

• If a urine specimen will be collected, give the patient a urine container the evening before so that she can provide a first voided morning specimen. This specimen generally contains the greatest concentration of hCG.

During

• Collect the first-voided urine specimen for urine testing.

• Collect a venous blood sample in a red-top tube for serum testing. Avoid hemolysis.

 After

 • Apply pressure to the venipuncture site.

* Emphasize to the patient the importance of antepartal health care.

 Abnormal findings

 Increased levels

- Pregnancy

- Ectopic pregnancy

- Hydatidiform mole of the uterus

- Choriocarcinoma of the uterus, testes, or ovaries

- Tumor

Decreased levels

- Spontaneous abortion

- Fetal death

- Ectopic pregnancy

مواضيع ذات صلة

human T-cell lymphotropic virus (HTLV) I/II antibody

human placental lactogen (hPL, Human chorionic somatomammotropin [HCS])

human papillomavirus (HPV test, HPV DNA testing, HPV Genotyping, HPV mRNA testing)

human lymphocyte antigen B27 (HLA-B27 antigen, Human leukocyte A antigen, White blood cell antigens, Histocompatibility leukocyte A antigen)

Nucleic Acid –Based Tests

homocysteine (Hcy)

HIV serologic and virologic testing

HIV RNA quantification (HIV viral load)

Molecules involved in Lipoprotein metabolism

Lipoproteins

Retinol Binding Protein

Direct Visualization Of The Organism