Lyme, Mono, ANA, Pregnancy

Question 1

What is the Lyme Disease Titer used for? Normal value?

Answer 1

Test used to diagnose Lyme disease.

Normal is negative with low titers of IgM and IgG antibodies

Question 2

What is Lyme disease caused by?

Answer 2

Lyme disease is caused by the spirochete Borrelia burgdorferi transmitted by the deer tick. Cultures can isolate the spirochete in half the cases but it is difficult to culture and takes a long time to grow.

Question 3

When do the IgM and IgG antibodies peak in Lyme disease?

Answer 3

IgM antibody peaks during the 3rd-6th week after disease onset and then gradually decreases.

Titers of IgG antibodies are low during the first several weeks of illness and reach maximum levels 4-6 months later.

Question 4

What are the interfering factors for the Lyme disease test?

Answer 4

Previous infection with B. burgdorferi can cause positive results even though they no longer have Lyme disease. Other spirochete diseases can cause false positive results

Question 5

What is the Mononucleosis Spot Heterophil antibody test used for?

Answer 5

Rapid test to assist in diagnosis of infectious mononucleosis, caused by the Epstein-Barr virus (EBV)

Question 6

When is infectious mono considered?

Answer 6

When antibodies are present in dilutions of > 1:56, infectious mono can be considered.

Question 7

Who does mono usually affect? Symptoms, findings?

Answer 7

Mono usually affects young adults with a presentation of fever, pharyngitis, lymphadenopathy, and splenomegaly.

Two weeks after onset of disease, many patients have IgM heterophil antibodies in their serum that react against warm RBCs.

Question 8

When can false positives of the Mononucleosis Spot Heterophil antibody test occur?

Answer 8

False positive results can occur in other diseases that cause elevation of heterophil antibodies, including lymphoma, lupus, Burkitt lymphoma, leukemia, and some GI cancers

Question 9

What must the diagnosis of mono include?

Answer 9

Diagnosis of mono must include a clinical presentation compatible with mono, lymphocytosis, atypical lymphocytes, and a positive serologic test

Question 10

What can caused an increased level of theMononucleosis Spot Heterophil antibody?

Answer 10

Increased levels occur in infectious mononucleosis, chronic EBV infection, chronic fatigue syndrome, Burkitt lymphoma, some forms of chronic hepatitis

Question 11

What is the Antinuclear Antibody (ANA) test used for? Normal values?

Answer 11

Used to diagnose systemic lupus erythematosus (SLE) and other autoimmune diseases.

Primarily used to screen for SLE – almost all patients with SLE develop autoantibodies, so a negative ANA excludes the disease.

If ANA is positive then other antibody studies must be done to confirm the diagnosis.

Normal: negative at 1:40 dilution

Question 12

How sensitive and specific is the Antinuclear Antibody (ANA) test ?

Answer 12

ANA is a group of protein antibodies that react against cellular nuclear material and is quite sensitive for detecting SLE with positive results in 95% of patients with the disease.

Other rheumatic diseases are also associated with ANA so it is not a specific test for SLE

Question 13

What are the Interfering factors for the Antinuclear Antibody (ANA) test ?

Answer 13

Drugs that cause false positive ANA test include acetazolamide, aspirin, chlorothiazides, hydralazine, penicillin, phenytoin, procainamide, sulfonamides, and tetracyclines

Drugs that cause false negative test include steroids

Question 14

What cause increased levels of the Antinuclear Antibody (ANA)?

Answer 14

SLE

Rheumatoid arthritis – autoimmune response targeted to synovial tissues

Polyarteritis nodosa – autoimmune response targeted to small vessels of various organs

Dermatomyositis, Polymyositis – autoimmune response targeted to skeletal muscle

Scleroderma – autoimmune response targeted to endothelium of blood vessels leading to fibrosis

Sjogren syndrome – autoimmune response targeted to exocrine glands (lacrimal and salivary)

Raynaud phenomenon
Other immune diseases, leukemia, infectious mono, myasthenia gravis, cirrhosis, chronic hepatitis

Question 15

What is the pregnancy test (Human Chorionic Gonadotropin -hCG) used for? Normal values?

Answer 15

Used to diagnose pregnancy.

Also used to monitor high risk pregnancies and can be used as a tumor marker for certain cancers.

Normal findings:
Qualitative – negative, positive in pregnancy
Quantitative – depends on number of weeks gestation

Question 16

What is hCG?

Answer 16

All pregnancy tests are based on the detection of hCG, which is secreted by the placental trophoblast after the ovum is fertilized.

It appears in the blood and urine as early as 10 days after conception.

In the first few weeks of pregnancy, hCG markedly rises and serum levels are higher than urine. After a month the levels are about the same.

Levels usually double every 48 hours

Question 17

What are the Interfering factors for pregnancy tests?

Answer 17

Tests performed too early in the pregnancy may give false negative results due to lack of significant hCG.

Hematuria and proteinuria may cause false positive results.

Hemolysis of blood may interfere with results.

Urine pregnancy tests vary according to dilution of the urine. hCG may be undetectable in a dilute specimen.

Drugs that may cause false negative urine results include diuretic and promethazine

Drugs that may cause false positive results include anticonvulsants, antiparkinsonian drugs, hypnotics, and tranquilizers

Question 18

What causes increased levels of hCG?

Answer 18

Pregnancy, ectopic pregnancy – highest levels are recorded in pregnancy, lowest levels seen in ectopic pregnancy.

Hydatidiform mole of the uterus, choriocarcinoma of uterus, germ cell tumors of testes or ovaries, other tumors (hepatoma and lymphoma) – hCG produced in variable amounts. Serial monitoring of hCG in these tumors probably more important than the initial test result

Question 19

What causes decreased levels of hCG?

Answer 19

Decreased levels seen in threatened abortion, incomplete abortion, dead fetus – diminished viability of the placenta, which produces hCG in pregnancy

Normally hCG is not present in nonpregnant women