Sorted By Test Name - Mayo Medical Laboratories

SFZ
8238
identify allergens which may be responsible for allergic disease and/or anaphylactic episode, to confirm
sensitization to particular allergens prior to beginning immunotherapy, and to investigate the specificity of
allergic reactions to insect venom allergens, drugs, or chemical allergens.
Interpretation: Detection of IgE antibodies in serum (Class 1 or greater) indicates an increased
likelihood of allergic disease as opposed to other etiologies and defines the allergens that may be
responsible for eliciting signs and symptoms. The level of IgE antibodies in serum varies directly with the
concentration of IgE antibodies expressed as a class score or kU/L.
Reference Values:
Class IgE kU/L Interpretation
0 Negative
1 0.35-0.69 Equivocal
2 0.70-3.49 Positive
3 3.50-17.4 Positive
4 17.5-49.9 Strongly positive
5 50.0-99.9 Strongly positive
6 > or =100 Strongly positive Reference values
apply to all ages.
Clinical References: Homburger HA: Allergic diseases. In Clinical Diagnosis and Management by
Laboratory Methods. 21st edition. Edited by RA McPherson, MR Pincus. New York, WB Saunders
Company, 2007, Chapter 53, Part VI, pp 961-971
Sulfamethoxazole, Serum
Clinical Information: Sulfamethoxazole is a sulfonamide antibiotic that is administered in
conjunction with another antibacterial, trimethoprim. These agents are used to treat a variety of infections
including methicillin-resistant Staphylococcus aureus, and for prophylaxis in immunosuppressed patients
such as HIV-positive individuals. Therapeutic drug monitoring is not commonly performed unless there
are concerns about adequate absorption, clearance, or compliance. Monitoring of sulfamethoxazole is
indicated only when prolonged (>3 months) therapy is required. Sulfamethoxazole is absorbed readily
after oral administration, with peak serum concentration occurring 2 to 3 hours after an oral dose. Its
average elimination half-life is 6 to 10 hours. Toxicity includes crystalluria with resultant calculi and renal
disease. Toxicity is due to a high concentration of acetylated, relatively insoluble forms of the drug.
Excess fluid should be taken with sulfamethoxazole to avoid formation of urine sulfonamide crystals.
Useful For: Monitoring therapy to ensure drug absorption, clearance, or compliance
Interpretation: Serum drug concentrations should be interpreted with respect to the minimum
inhibitory concentration (MIC) of targeted organisms. Most patients will display peak steady-state serum
concentrations >50 mcg/mL when drawn at least 1 hour after an oral dose. Targets concentrations may be
higher, depending on the intent of therapy. Toxicity (formation of urinary crystals) associated with
sulfamethoxazole occurs with prolonged exposure to serum concentrations >125 mcg/mL.
Reference Values:
>50 mcg/mL
Clinical References: 1. Young T, Oliphant C, Araoyinbo I, Volmink J: Co-trimoxazole prophylaxis
in HIV: the evidence. S Afr Med J 2008;98(4):258-259 2. Avdic, Cosgrove: Management and control
strategies for community-associated methicillin-resistant Staphylococcus aureus. Expert Opin
Pharmacother 2008;9(9):1463-1479 3. Kamme C, Melander A, Nilsson N: Serum and saliva
concentrations of sulfamethoxazole and trimethoprim in adults in children: relation between saliva
concentrations and in vitro activity against nasopharyngeal pathogens. Scand J Infect Dis
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