Sorted By Test Name - Mayo Medical Laboratories

FDM
90117
DME
60480
Dextromethorphan (DM), Serum
Reference Values:
Reference Range: 2.0-6.0 ng/mL
Test Performed By
Medtox Laboratories, Inc.
402 W County Road D
St. Paul, MN 55112
Diabetes Mellitus Type 1 Evaluation
Clinical Information: Islet cell autoantibodies were first recognized to be associated with type 1
diabetes mellitus in 1974. Several islet cell-specific autoantigens have been identified in recent years.(1)
These include glutamic acid decarboxylase 65 (GAD65), the tyrosine phosphatase-related islet antigen 2
(IA-2), and insulin. The sensitivities of these autoantibodies for type 1 diabetes in an international
collaborative study were 91% (GAD65 antibody), 74% (IA-2 antibody), and 49% (insulin antibody) when
tested in isolation.(2) When tested in combination, the combined sensitivity for type 1 diabetes was up to
98%, with a specificity of 98% to 100%. (2) These autoantibodies also are detectable before the clinical
onset of diabetes. Prospective studies in relatives of patients with type 1 diabetes have shown that the
detection of 1 or more islet autoantibodies is an early marker of progression to type 1 diabetes. Among
first-degree relatives of those with type 1 diabetes, the cumulative risk of developing diabetes at 5 years
after testing was 17% if seropositive for 1 antibody, 39% if seropositive for 2 antibodies, and 70% if
seropositive for 3 antibodies.(3) Autoantibody profiles identifying patients destined to develop type 1
diabetes are usually detectable in serum before age 3. Some patients with type 1 diabetes are initially
misdiagnosed as having type 2 diabetes because of symptom onset in adulthood, societal obesity, and
initial insulin-independence. Detection of 1 or more islet autoantibodies allows identification of patients
with "latent autoimmune diabetes in adulthood" amongst those with presumed type 2 diabetes.
Useful For: Distinguishing type 1 from type 2 diabetes mellitus Identifying individuals at risk of type 1
diabetes (including high-risk relatives of patients with diabetes) Predicting future insulin requirement
treatment in patients with adult-onset diabetes
Interpretation: Seropositivity for 1 or more islet cell autoantibodies is supportive of: -A diagnosis of
type 1 diabetes. Only 2% to 4% of patients with type 1 diabetes are antibody negative; 90% have more
than 1 antibody marker, and 70% have 3 markers.(1) Patients with gestational diabetes who are antibody
seropositive are at high risk for diabetes postpartum. Rarely, diabetic children test seronegative, which
may indicate a diagnosis of maturity-onset diabetes of the young in clinically suspicious cases. -A high
risk for future development of diabetes. Among 44 first degree relatives of patients with type 1diabetes,
those with 3 antibodies had a 70% risk of developing type 1 diabetes within 5 years.(3) -A current or
future need for insulin therapy in patients with diabetes. In the UK Prospective Diabetes Study, 84% of
those classified clinically as having type 2 diabetes and seropositive for glutamic acid decarboxylase 65
required insulin within 6 years, compared to 14% that were antibody negative.(4)
Reference Values:
GLUTAMIC ACID DECARBOXYLASE (GAD65) ANTIBODY
< or =0.02 nmol/L
Reference values apply to all ages.
INSULIN ANTIBODIES
< or =0.02 nmol/L
Reference values apply to all ages.
ISLET ANTIGEN 2 (IA-2) ANTIBODY
< or =0.02 nmol/L
Reference values apply to all ages.
Current as of January 4, 2013 7:15 pm CST 800-533-1710 or 507-266-5700 or MayoMedicalLaboratories.com Page 611