22 Laboratory studies Flashcards
What are the only Ag-specific for syphilis
FTA-ABS, MHA-TA
What test is used to screen for syphilis
VDRL
T/F: FTA-ABS become negative once pt has been adequately tx for syphilis
False
What are some common labs in pts with sarcoidosis
Hypergammaglobulinemia, elevated LFTs, Ca, ESR, and ACE
What is an abnl Schirmer test
Less than 5 mm wetting after 5 mins; less than 10 mm wetting after stimulation with 10% ammonia
What tests used to dx Sjogren’s
Minor salivary gland bx showing mononuclear cell infiltration, SSA, SSB, ANA, RF
What lab test is a/w lymphoproliferative malignancy in pts w/ Sjogrens
Decreased level of serum IgM
Lab findings in pt with relapsing polychondritis
Elevated ESR, moderate leukocytosis, mild-to-mod anemia
What lab test is most specific for Wegener’s
c-ANCA
What is the significance of a rising c-ANCA titer in pt w/ Wegener’s
Usu indicates a relapse of active dz
HLA-DW4 Ab are m/c seen in which autoimmune dz
RA
What auto-Ab is present in 75% of pts with RA
RF
What is the most specific test for the dx of autoimmune SNHL
Western blot assay for 68 kD inner ear antigen (Otoblot) (95% specific)
The 68 kDa Ag is thought to represent what protein
Heat shock protein 70
What percent of pts with immune-mediated Meniere’s dz will have a positive anti-68-kD western blot test
30-50%
What is the most specific test for the dx of Cogan’s syndrome
Western blot assay for 55 kD inner ear antigen
Pt w/ Cogan’s syndrome usu have elevated titers to what organism
Chlamydia
What is the latency period for developing antibodies to hepatitis C
up to 4 months
What is the latency period for seroconversion following exposure to HIV
6-12 months
What adjunctive test should be performed in a female with suspected JNA
chromosome analysis
What test is used to dx pertussis
Cx from NP using a Dacron or calcium alginate swab placed on a Regan-Lowe or Bordet-Gengou agar plate
What is the sensitivity of this test
80% (less if already on antibiotics)
What tests confirm the dx of infectious mono
Blood smear showing atypical mononuclear cells and a positive Paul-Bunnell test (elevated heterophile titer of EBV)
What is most useful study of non-TB mycobacterial adenitis of H&N region in kids
Cx
What test should be performed in a pt w/ suspected AFS who does not have classic findings on CT scan or + middle meatal cx
aspergillus skin test and precipitins
How is congenital CMV dx in newborn
ID of serum anti-CMV IgM, “owl-eye” bodies in urinary sediment, and intracerebral calcifications on radiographs
What is most accurate method of determining if otorrhea is CSF
B2 transferrin
What are the characteristics of CSF in presence of meningitis
Elevated protein, WBC, and pressure; dec GLC
What lab tests can be used to dx CSF leak
Measurement of GLC (nasal secretions are devoid of GLC), B2 transferrin
What is the single best measure of nutritional status
serum albumin level
What serum albumin level is a/w malnutrition
Less than 3 g/dL
Which serum proteins can be used to assess short-term nutritional status
Transferrin (1/2 life 8-9 days), prealbumin (1/2 life 2 days), retinal-binding globulin (1/2 life 12 hrs)
All pts w/ paraganglioma should be tested for mutations in which gene?
SDH (succinate dehydrogenase)
What are the m/c immunologic findings among pts with NP CA
Elevated IgA and IgG Ab against the viral capsid Ag of EBV
What is the role of EBV titers in pts with NP CA
“May be a valuable screening tool in high-risk populations and can help establish the diagnosis of NPC in the patient with an unknown primary. In patients with type I disease, EBV titers are not elevated and have no prognostic significance.
“What percent of patients with WHO types II and III tumors have abnormally increased titers to EBV VCA and NA?
80-90%
What test provides prognostic info in pts with NP CA
Antibody-dependent cellular cytotoxicity (ADCC) assay
How does this assay predict survival
low levels are a/w worse prog
How do you test for multiple myeloma in pt with extramedullary plasmacytoma
Measure serum M-protein and urine Bence Jones protein; bone survey; bone marrow bx
What test is used to distinguish a hypothalamic defect from a pituitary defect in a pt w/ hypothyroidism
The thyrotopin-releasing hormone (TRH) stimulation test
T/F: thyroglobulin levels should be obtained prior to performing FNA on a thyroid nodule
True: FNA will falsely elevate thyroglobulin levels
What is the purpose of obtaining a thyroglobulin level prior to thyroidectomy
It has been shown to correlate well with histologic tumor type and is useful as a marker for tumor recurrence
What test should be ordered in pt w/ elevated TSH
Antimicrosomal Ab (antithyroperoxidase level) to r/o Hashimoto’s thyroiditis
What lab test should be obtained in pts with FMH of medullary thyroid carcinoma
Calcitonin
What lab w/u is needed in pts with MTC
Basal and pentagastrin stimulated calcitonin levels, serum CA, 24 hr urine catecholamines, VMA, and metanephrine, +/- CEA
What are the histochemical characteristics of MTC
Congo red dye positive, apple-green birefringence consistent with amyloid; immunohistochemistry positive for cytokeratins, CEA, and calcitonin.
What is the false negative rate of RET analysis
5%
What is the most accurate test for dx of primary HPTH
Measurement of intact PTH
Why is measurement of C-terminal of PTH not accurate for dx of 2ndary HPTH
“C-terminal fragments are cleared by the kidney; elevation may indicate either renal insufficiency or hyperparathyroidism.”
“What is the difference in the Ca/Cr clearance ratio in someone with FHH and someone with primary hyperparathyroidism?
“Ca/Cr clearance <0.01 in FHH; >0.02 in primary hyperparathyroidism.
