Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1071 page)

   Use

   MPV is used to evaluate variations in platelet size as related to various platelet abnormalities.

   Interpretation

Increased In

   Hypothyroidism

   Myeloproliferative neoplasms

   All cases of accelerated bone marrow production of platelets (immune thrombocytopenias, postchemotherapy)

   Bernard-Soulier syndrome

Decreased In

   Disorders associated with decreased platelet production

   In some patients with sepsis

   In some patients with inherited thrombocytopenias, such as Wiskott-Aldrich syndrome

   Limitations

   Reference values appear to vary with the platelet count. MPV is affected by numerous variables related to specimen collection, the anticoagulant used, temperature, and duration of storage.

METANEPHRINES, URINE

   Definition

   Metanephrine and normetanephrine are metabolic products of epinephrine and norepinephrine, the adrenal medullary hormones secreted by pheochromocytomas. Fractionated tests provide higher diagnostic sensitivity than assays for total catecholamines.