Test Directory - Understand Your Tests.

X-linked Agammaglobulinemia (XLA): BTK (Full Gene Sequencing)

Test Includes

This test covers all coding nucleotides of gene BTK, plus at least two and typically 20 flanking intronic nucleotides upstream and downstream of each coding exon, covering the conserved donor and acceptor splice sites, as well as typically 20 flanking nucleotides in the 5′ and 3′ UTR.

Special Instructions

In cases in which a known mutation can be documented, the physician may prefer to order test 252683. Test orders must include an attestation that the provider has the patient's informed consent for genetic testing. See sample physician office consent form: Consent for Genetic Testing. In the case of family tests (ie, known mutations), please submit the result report of the first patient tested in the family (the index case), if not performed at a LabCorp facility. Other family members are subsequently tested for the specific mutation found in the first patient tested.

Expected Turnaround Time

24 - 35 days

Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.

Specimen Requirements

Specimen

Whole blood; DNA is accepted (Call 800-345-4363 for DNA collection information.)

Volume

2 mL

Container

Lavender-top (EDTA) tube

Collection

Samples may be stored for brief periods at 4°C. Ship overnight at room temperature.

Storage Instructions

Maintain specimen at room temperature.

Causes for Rejection

Container broken or leaking; container not labeled or label not legible; improper anticoagulant

Test Details

Use

Confirm a clinical diagnosis of XLA; detect carriers; allow early diagnosis in family members, guiding prophylactic measures

Limitations

This method does not reliably detect mosaic variants; large deletions; large duplications, inversions, or other rearrangements; or deep intronic variants. It may be affected by allele-dropout, it may not allow determination of the exact numbers of T/A or microsatellite repeats, and it does not allow any conclusion as to whether two heterozygous variants are present on the same or on different chromosome copies. Results of this test are for investigational purposes only. The performance characteristics of this assay have been determined by LabCorp. The result should not be used as a diagnostic procedure without confirmation of the diagnosis by another medically established diagnostic product or procedure.

Methodology

DNA sequencing

Reference Interval

Normal equals reference sequence or variants that are known or predicted to be benign; abnormal equals all other variants.

Additional Information

X-linked agammaglobulinemia (XLA), also know as Bruton's agammaglobulinemia, is a male-limited X-linked recessive immune disorder characterized by almost complete absence of mature B cells and thus the inability to produce immunoglobulins of any class. Patients experience increased susceptibility to bacterial infections and reduced ability to resolve infections with enteroviruses such as echo, coxsackie, or poliovirus, which can then lead to slowly progressing, fatal disease affecting the central nervous system. Mutations in BTK account for all XLA and about 85% of all primary defects in early B-cell development. Genetic testing can confirm a clinical diagnosis of XLA and detect mutation carriers within affected families.

X-linked Agammaglobulinemia (XLA): BTK (Known Mutation)

Test Includes

All coding nucleotides of the specified gene(s), plus at least two and typically 20 nucleotides flanking each coding region.

Special Instructions

This option is available when the mutation is known and can be documented by the ordering physician. If the mutation cannot be documented, please order test 252453. Test orders must include an attestation that the provider has the patient's informed consent for genetic testing. See sample physician office consent form: Consent for Genetic Testing. In the case of family tests (ie, known mutations), please submit the result report of the first patient tested in the family (the index case), if not performed at a LabCorp facility. Other family members are subsequently tested for the specific mutation found in the first patient tested.

Expected Turnaround Time

21 - 28 days

Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.

Test Details

Methodology

DNA sequencing

X-linked Lymphoproliferative Disease (XLP): SH2D1A (Full Gene Sequencing)

Test Includes

This test covers all coding nucleotides of gene SH2D1A, plus at least two and typically 20 flanking intronic nucleotides upstream and downstream of each coding exon, covering the conserved donor and acceptor splice sites, as well as typically 20 flanking nucleotides in the 5′ and 3′ UTR.

Special Instructions

In cases in which a known mutation can be documented, the physician may prefer to order test 252740. Test orders must include an attestation that the provider has the patient's informed consent for genetic testing. See sample physician office consent form: Consent for Genetic Testing. In the case of family tests (ie, known mutations), please submit the result report of the first patient tested in the family (the index case), if not performed at a LabCorp facility. Other family members are subsequently tested for the specific mutation found in the first patient tested.

Expected Turnaround Time

28 - 35 days

Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.

Specimen Requirements

Specimen

Whole blood; DNA is accepted (Call 800-345-4363 for DNA collection information.)

Volume

2 mL

Container

Lavender-top (EDTA) tube

Collection

Samples may be stored for brief periods at 4°C. Ship overnight at room temperature.

Storage Instructions

Maintain specimen at room temperature.

Causes for Rejection

Container broken or leaking; container not labeled or label not legible; improper anticoagulant

Test Details

Use

Confirm a clinical diagnosis of XLP; detect carriers; allow early diagnosis in family members

Limitations

This method does not reliably detect mosaic variants; large deletions; large duplications, inversions, or other rearrangements; or deep intronic variants. It may be affected by allele-dropout, it may not allow determination of the exact numbers of T/A or microsatellite repeats, and it does not allow any conclusion as to whether two heterozygous variants are present on the same or on different chromosome copies. Results of this test are for investigational purposes only. The performance characteristics of this assay have been determined by LabCorp. The result should not be used as a diagnostic procedure without confirmation of the diagnosis by another medically established diagnostic product or procedure.

Methodology

DNA sequencing

Reference Interval

Normal equals reference sequence or variants that are known or predicted to be benign; abnormal equals all other variants.

Additional Information

X-linked lymphoproliferative disease (XLP), also known as Duncan's disease, is an X-linked recessive immune disorder characterized by fulminant infectious mononucleosis (FIM), dysgammaglobulinemia, and/or lymphoproliferative disorders. FIM, which occurs in response to infection with Epstein-Barr virus, affects approximately 60% of XLP patients and is the most severe manifestation, often leading to death within one to two months. Dysgammaglobulinemia affects about 30% of patients, and malignant and nonmalignant lymphomas occur in 20% to 30% of XLP patients. To date, mutations in SH2D1A are the only known cause of XLP. Genetic testing can confirm a clinical diagnosis of XLP and detect mutation carriers within affected families.

X-linked Lymphoproliferative Disease (XLP): SH2D1A (Known Mutation)

Test Includes

All coding nucleotides of the specified gene(s), plus at least two and typically 20 nucleotides flanking each coding region.

Special Instructions

This option is available when the mutation is known and can be documented by the ordering physician. If the mutation cannot be documented, please order test 252535. Test orders must include an attestation that the provider has the patient's informed consent for genetic testing. See sample physician office consent form: Consent for Genetic Testing. In the case of family tests (ie, known mutations), please submit the result report of the first patient tested in the family (the index case), if not performed at a LabCorp facility. Other family members are subsequently tested for the specific mutation found in the first patient tested.

Expected Turnaround Time

21 - 28 days

Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.

Test Details

Methodology

DNA sequencing

Xylose Tolerance Test (Fasting + One-hour Blood + Five-hour Urine−Pediatric)

Synonyms

d-Xylose Tolerance Test

Test Includes

Fasting plasma xylose, one-hour (child) postdose plasma xylose, plus five-hour urine xylose

Special Instructions

Record five-hour urine total volume on the request form.

Expected Turnaround Time

4 - 6 days

Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.

Related Information

Urine Specimens

Specimen Requirements

Specimen

Plasma and urine

Volume

2 mL plasma (each specimen) and 10 mL aliquot of five-hour urine

Minimum Volume

0.6 mL plasma (each specimen) and 0.5 mL aliquot of five-hour urine

Container

Gray-top (sodium fluoride) tube and plastic urine container

Collection

Pediatric: Plasma: Draw fasting and one-hour postdose blood samples (See Patient Preparation). Centrifuge and separate plasma from cells immediately. Indicate time drawn (ie, "fasting", "one-hour") on each plasma tube. Urine: Collect entire five-hour urine volume. Send aliquot.

Storage Instructions

Refrigerate plasma. Maintain urine specimen at room temperature. Urine sample is stable for 14 days at room temperature, refrigerated, or frozen. It is stable for two freeze/thaw cycles.

Patient Preparation

Patient must fast a minimum of eight hours prior to administration of d-xylose (LabCorp N° 26599, containing 25 g d-xylose). Pediatric patients (younger than nine years) must be fasting for at least four hours. Patient must remain in supine position for duration of test except during urine collection. No food is permitted during the test. Patient should refrain from eating foods containing pentose and medications (especially aspirin, neomycin, colchicine, indomethacin, or atropine) for 24 hours prior to the test. Foods containing pentose include fruits, jams, jellies, and pastries. No water restriction; in fact, patient should be encouraged to drink during the fasting period and during test. Start test in the AM. Instruct patient to void completely. Discard this urine. Draw fasting blood specimen. Weight-based dosage of d-xylose for oral administration: 0.5 g/kg body weight up to a maximum of 25 g. Dissolved in water 10% (w/v) with a maximum of 250 mL. Have patient drink entire amount. Fill cup with 250 mL water and have patient drink this also. Have patient drink another cup with 250 mL water after one hour. Collect urine for five hours after administration of d-xylose. Record total five-hour urine volume and send aliquot. Record total on the request form. Draw remaining blood specimens (children: one hour).

Causes for Rejection

Plasma specimen not kept chilled; patient vomits test meal; loss of part of urine specimen and/or contaminated with stool

Test Details

Use

Evaluate possible enterogenous malabsorption syndromes; test for functional integrity of the jejunum

Limitations

This test was developed, and its performance characteristics determined, by LabCorp. It has not been cleared or approved by the Food and Drug Administration.

Methodology

Spectrophotometry

Reference Interval

• Plasma: One hour: children: >30 mg/dL • Urine: Children: 16% to 33% of ingested dose

Additional Information

Xylose is a pentose found naturally occurring in certain fruits such as plums. It is not normally found in significant concentrations in blood or urine thereby rendering the duodenojejunal absorption of d-xylose a useful mechanism to assess the integrity of the gastrointestinal mucosa. D-xylose is passively absorbed by the small bowel with some 30% to 40% of the ingested dose rapidly excreted in the urine. Absorption into the blood is evaluated at specific time intervals with intestinal malabsorption being indicated by low absorption values. Low values would likewise be seen in celiac diseases, tropical sprue, Crohn's disease, immunoglobulin deficiency, pellagra, ascariasis, blind loop syndrome, radiation enteritis, surgical bowel resection, vomiting, delayed gastric emptying, inadequate hydration, decreased circulation, intrinsic renal disease, thyroid disease, ascites, and increased intestinal motility from any cause. The d-xylose absorption test may be of some help in distinguishing pancreatic insufficiency from jejunal malabsorption. Essentially normal d-xylose absorption values will be obtained in malabsorption values due to pancreatic insufficiency, whereas low blood values will be obtained in jejunal malabsorption. Urine values for xylose excretion are useful in determining renal insufficiency. Diminished excretion of d-xylose could be indicative of renal insufficiency, thereby invalidating the blood xylose absorption results. Low urine xylose values could also be attributed to incomplete collection or urinary retention.

Aftercare

May cause mild diarrhea

Xylose Tolerance Test (Fasting + One-hour Blood Without Five-hour Urine−Pediatric)

Special Instructions

Please refer to test 293811 and the directions for Sequential Sampling.

Expected Turnaround Time

3 - 4 days

Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.

Specimen Requirements

Specimen

Plasma

Volume

0.6 mL (each specimen)

Minimum Volume

0.6 mL (each specimen)

Xylose Tolerance Test (Fasting + Two-hour Blood + Five-hour Urine−Adult)

Synonyms

d-Xylose Tolerance Test

Test Includes

Fasting plasma xylose, two-hour (adult) postdose plasma xylose, plus five-hour urine xylose

Special Instructions

Record five-hour urine total volume on the request form.

Expected Turnaround Time

4 - 6 days

Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.

Related Information

Urine Specimens

Specimen Requirements

Specimen

Plasma and urine

Volume

2 mL plasma (each specimen) and 10 mL aliquot of five-hour urine

Minimum Volume

0.6 mL plasma (each specimen) and 0.5 mL aliquot of five-hour urine

Container

Gray-top (sodium fluoride) tube and plastic urine container

Collection

Adults: Plasma: Draw fasting and two-hour postdose blood samples (see Patient Preparation). Centrifuge and separate plasma. Indicate time drawn (ie, "fasting", "two-hour") on tubes. Urine: Collect entire five-hour urine volume. Send aliquot.

Storage Instructions

Refrigerate plasma. Maintain urine specimen at room temperature. Urine sample is stable for 14 days at room temperature, refrigerated, or frozen. It is stable for two freeze/thaw cycles.

Patient Preparation

Patient must fast a minimum of eight hours prior to administration of d-xylose (LabCorp N° 26599, containing 25 g d-xylose). Patient must remain in supine position for duration of test except during urine collection. No food is permitted during the test. Patient should refrain from eating foods containing pentose and medication especially aspirin, neomycin, colchicine, indomethacin, or atropine for 24 hours prior to the test. These include fruits, jams, jellies and pastries containing these items. No water restriction; in fact, patient should be encouraged to drink during the fasting period and during test. Start test in the AM. Instruct patient to void completely. Discard this urine. Draw fasting blood specimen. Weight-based dosage of d-xylose for oral administration: 0.5 g/kg body weight up to a maximum of 25 g. Dissolved in water 10% (w/v) with a maximum of 250 mL. Have patient drink entire amount. Fill cup with 250 mL water and have patient drink this also. Have patient drink another cup with 250 mL water after one hour. Collect urine for five hours after administration of d-xylose. Record total five-hour urine volume and send aliquot. Record total on the request form. Draw remaining blood specimens (adults: two hours).

Causes for Rejection

Plasma specimen not kept chilled; patient vomits test meal; loss of part of urine specimen and/or contaminated with stool

Test Details

Use

Evaluate possible enterogenous malabsorption syndromes; test for functional integrity of the jejunum

Limitations

This test was developed, and its performance characteristics determined, by LabCorp. It has not been cleared or approved by the Food and Drug Administration.

Methodology

Spectrophotometry

Reference Interval

• Plasma: 2 hours: 32-58 mg/dL • Urine: Adults 65 years or younger: >4.0 g/5 hours; adults older than 65 years: >3.5 g/5 hours

Additional Information

Xylose is a pentose found naturally occurring in certain fruits such as plums. It is not normally found in significant concentrations in blood or urine thereby rendering the duodenojejunal absorption of d-xylose a useful mechanism to assess the integrity of the gastrointestinal mucosa. d-Xylose is passively absorbed by the small bowel with some 30% to 40% of the ingested dose rapidly excreted in the urine. Absorption into the blood is evaluated at specific time intervals with intestinal malabsorption being indicated by low absorption values. Low values would likewise be seen in celiac diseases, tropical sprue, Crohn's disease, immunoglobulin deficiency, pellagra, ascariasis, blind loop syndrome, radiation enteritis, surgical bowel resection, vomiting, delayed gastric emptying, inadequate hydration, decreased circulation, intrinsic renal disease, thyroid disease, ascites, and increased intestinal motility from any cause. The d-xylose absorption test may be of some help in distinguishing pancreatic insufficiency from jejunal malabsorption. Essentially normal d-xylose absorption values will be obtained in malabsorption values due to pancreatic insufficiency, whereas low blood values will be obtained in jejunal malabsorption. Urine values for xylose excretion are useful in determining renal insufficiency. Diminished excretion of d-xylose could be indicative of renal insufficiency, thereby invalidating the blood xylose absorption results. Low urine xylose values could also be attributed to incomplete collection or urinary retention.

Aftercare

May cause mild diarrhea.

Xylose Tolerance Test (Fasting + Two-hour Blood Without Five-hour Urine−Adult)

Special Instructions

Please refer to test 293837 and the directions for Sequential Sampling.

Expected Turnaround Time

4 - 6 days

Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.

Specimen Requirements

Specimen

Plasma

Volume

2 mL (each specimen)

Minimum Volume

1 mL (each specimen)

Test Details

Limitations

This test was developed, and its performance characteristics determined, by LabCorp. It has not been cleared or approved by the Food and Drug Administration

Xylose Tolerance Test (Fasting, One-, Two-, Three-, Four-, and Five-hour Blood + Five-hour Urine)

Synonyms

d-Xylose Tolerance

Test Includes

Specimens drawn fasting, one, two, three, four, and five hours plus five-hour urine xylose result

Special Instructions

Record total five-hour urine volume on the test request form.

Related Information

Urine Specimens

Specimen Requirements

Specimen

Plasma and urine

Volume

2 mL plasma (each specimen) and 10 mL aliquot of five-hour urine

Minimum Volume

0.6 mL plasma (each specimen) and 0.5 mL aliquot of five-hour urine

Container

Gray-top (sodium fluoride) tube and plastic urine container

Collection

Plasma: Draw fasting sample, administer d-xylose dose (see Patient Preparation), and obtain one-, two-, three-, four-, and five-hour samples postdose. Centrifuge and separate plasma from cells immediately. Indicate time drawn (ie, "fasting," "one-hour," etc) on each plasma tube submitted. Urine: Start test in AM. Instruct patient to void completely. Discard this sample. Collect urine for five hours after administration of d-xylose.

Storage Instructions

Refrigerate plasma. Maintain urine specimen at room temperature. Urine sample is stable for 14 days at room temperature, refrigerated, or frozen. It is stable for two freeze/thaw cycles.

Patient Preparation

Patient must fast a minimum of eight hours prior to administration of d-xylose (LabCorp N° 26599, containing 25 g d-xylose). Pediatric patients (younger than nine years of age) should fast only four hours. No restriction on water. Weigh patient for proper dosage of d-xylose. Patient must remain in supine position for duration of the test except during urine collection. Patient should refrain from foods rich in pentose (fruits, preserves, and grains) for a 24-hour period prior to the test. Weight-based dosage of d-xylose for oral administration: 0.5 g/kg body weight up to a maximum of 25 g. Dissolved in water 10% (w/v) with a maximum of 250 mL. Patient should drink eight ounces (250 mL) of water after d-xylose administration and another eight ounces after one hour. Record total five-hour urine volume and send aliquot. Record total on the test request form.

Causes for Rejection

Plasma specimens not kept chilled; patient vomits test meal; loss of part of urine specimen and/or contaminated with stool

Test Details

Use

Diagnose intestinal malabsorption syndromes

Limitations

This test was developed, and its performance characteristics determined, by LabCorp. It has not been cleared or approved by the Food and Drug Administration.

Methodology

Spectrophotometry

Reference Interval

• Plasma: − Children: 1 hour: >30 mg/dL − Adults: 1 hour: 21−57 mg/dL, 2 hours: 32−58 mg/dL, 3 hours: 19−42 mg/dL, 4 hours: 11−29 mg/dL, 5 hours: 6−18 mg/dL • Urine: − Children: 16% to 33% of ingested dose − Adults: 65 years or younger: >4.0 g/5 hours; older than 65 years: >3.5 g/5 hours

Aftercare

May cause mild diarrhea

Xylose Tolerance Test (Fasting, One-, Two-, Three-, Four-, and Five-hour Blood Without Five-hour Urine)

Special Instructions

Please refer to test 023374 and the directions for Sequential Sampling.

Expected Turnaround Time

3 - 4 days

Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.

Specimen Requirements

Specimen

Plasma

Volume

2 mL (each specimen)

Minimum Volume

0.6 mL (each specimen)

Test Includes

Special Instructions

Expected Turnaround Time

Related Documents

Specimen Requirements

Specimen

Volume

Container

Collection

Storage Instructions

Causes for Rejection

Test Details

Use

Limitations

Methodology

Reference Interval

Additional Information

Test Includes

Special Instructions

Expected Turnaround Time

Related Documents

Test Details

Methodology

Test Includes

Special Instructions

Expected Turnaround Time

Related Documents

Specimen Requirements

Specimen

Volume

Container

Collection

Storage Instructions

Causes for Rejection

Test Details

Use

Limitations

Methodology

Reference Interval

Additional Information

Test Includes

Special Instructions

Expected Turnaround Time

Related Documents

Test Details

Methodology

Synonyms

Test Includes

Special Instructions

Expected Turnaround Time

Related Information

Related Documents

Specimen Requirements

Specimen

Volume

Minimum Volume

Container

Collection

Storage Instructions

Patient Preparation

Causes for Rejection

Test Details

Use

Limitations

Methodology

Reference Interval

Additional Information

Aftercare

Special Instructions

Expected Turnaround Time

Related Documents

Specimen Requirements

Specimen

Volume

Minimum Volume

Synonyms

Test Includes

Special Instructions

Expected Turnaround Time

Related Information