Type of test Blood

Normal findings

 Female: 44 autosomes + 2 X chromosomes; karyotype: 46,XX

 Male: 44 autosomes + 1 X, 1 Y chromosome; karyotype: 46,XY

Test explanation and related physiology

This test is used to study an individual’s chromosomal makeup to determine chromosomal defects associated with disease or the risk of developing disease. The term karyotyping refers to the arrangement and pairing of cell chromosomes in order from the largest to the smallest to analyze their number and structure. Variations in either can produce numerous developmental abnormalities and diseases. A normal karyotype of chromosomes consists of a pattern of 22 pairs of autosomal chromosomes and a pair of sex chromosomes (XY for the male and XX for the female). Chromosomal karyotype abnormalities can be congenital or acquired. These karyotype abnormalities can occur because of duplication, deletion, translocation, reciprocation, or genetic rearrangement.

Chromosomal karyotyping is useful in evaluating congenital anomalies, mental retardation, growth retardation, delayed puberty, infertility, hypogonadism, primary amenorrhea, ambiguous genitalia, chronic myelogenous leukemia, neoplasm, recur rent miscarriage, prenatal diagnosis of serious congenital diseases (especially in situations of advanced maternal age), Turner syn drome, Klinefelter syndrome, Down syndrome, and other suspected genetic disorders. The products of conception also can be studied to determine the cause of stillbirth or miscarriage.

Procedure and patient care

Before

* Explain the procedure to the patient.

• Determine how the specimen will be collected. Obtain preparation guidelines from the laboratory if indicated.

 • Many patients are fearful of the test results and require considerable emotional support.

 • In some states, informed consent is required.

During

 • Specimens for chromosome analysis can be obtained from numerous sources. Leukocytes from a peripheral venipuncture are most easily and most often used for this study.

• Bone marrow biopsies and surgical specimens also can be used sometimes as sources for analysis.

• During pregnancy, specimens can be collected by amniocentesis and chorionic villus sampling .

• Fetal tissue or products of conception can be studied to deter mine the reason for loss of a pregnancy.

• Smears and stains of buccal mucosal cells are less costly but not as accurate as other tissue for karyotyping.

After

 • Aftercare depends on how the specimen was collected. Inform the patient that test results generally will not be available for several months.

• If an abnormality is identified, often the entire family line must be tested. This can be exhaustive and expensive. If the test results show an abnormality, encourage the patient to verbalize his or her feelings. Provide emotional support.

Abnormal findings

Congenital anomalies

 Mental retardation

 Growth retardation

 Delayed puberty

 Infertility

 Hypogonadism

 Primary amenorrhea

 Ambiguous genitalia

 Chronic myelogenous leukemia

 Neoplasm

 Recurrent miscarriage

 Trisomy 21 (Down syndrome)

 Tay–Sachs disease

 Sickle cell anemia

 Turner syndrome

 Klinefelter syndrome