Mayo Test Catalog, (Sorted By Test Name) - Mayo Medical ...

DIA
8629
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.
Clinical References: 1. Bingley PJ: Clinical applications of diabetes antibody testing. J Clin
Endocrinol Metab 2010;95:25-33 2. Verge CF, Stenger D, Bonifacio E, et al: Combined use of
autoantibodies (IA-2 autoantibody, GAD autoantibody, insulin autoantibody, cytoplasmic islet cell
antibodies) in type 1 diabetes: Combinatorial Islet Autoantibody Workshop. Diabetes 1998;47:1857-1866
3. Bingley PJ, Gale EA: Progression to type 1 diabetes in islet cell antibody-positive relatives in the
European Nicotinamide Diabetes Intervention Trial: the role of additional immune, genetic and metabolic
markers of risk. Diabetologia 2006;49:881-890 4. Turner R, Stratton I, Horton V, et al: UKPDS 25:
autoantibodies to islet-cell cytoplasm and glutamic acid decarboxylase for prediction of insulin
requirement in type 2 diabetes. UK Prospective Diabetes Study Group. Lancet 1997;350:1288-1293 5.
Masuda M, Powell M, Chen S, et al: Autoantibodies to IA-2 in insulin-dependent diabetes mellitus.
Measurements with a new immunoprecipitation assay. Clin Chim Acta 2000;291:53-66
Diazepam and Nordiazepam, Serum
Clinical Information: Benzodiazepine compounds, of which diazepam is a prototype, are widely
used as antianxiety, hypnotic, and muscle relaxant agents. Diazepam (Valium) also is frequently used to
treat status epilepticus, which is a state of rapidly recurring convulsive seizures that will not respond
immediately to conventional anticonvulsant therapy. Although diazepam has been the benzodiazepine of
choice for status epilepticus, recent evidence indicates that other drugs may be more beneficial because
they provide longer control of seizures and produce less cardiorespiratory depression. Patients develop
tolerance to diazepam, which requires that they be converted to phenobarbital or phenytoin within 24 to
48 hours of seizure control with diazepam. Diazepam is administered intravenously or intramuscularly at
a dose of 10 to 20 mg in adults to control recurrent seizures. It is rapidly absorbed, reaching peak plasma
concentrations in 1 hour. Drug elimination follows a biphasic pattern with a rapid phase of 2 to 3 hours
followed by a slow decay with a half-life of 2 to 8 days. After steady-state concentrations are achieved (in
about a week), a half-life of 3 to 4 days is found. Diazepam has a volume of distribution of 1.1 L/kg, a
half-life of 48 hours, and is 99% protein bound in serum. Nordiazepam is the major metabolite of
diazepam, tranxene, and prazepam, and can be differentiated from other benzodiazepines by gas-liquid
chromatography (GLC). Nordiazepam has a blood half-life of 4 to 5 days.
Useful For: Assessing compliance Monitoring for appropriate therapeutic level Assessing toxicity
Interpretation: For seizures: Serum concentrations are not usually monitored during early therapy
because response to the drug can be monitored clinically as seizure control. If seizures resume despite
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