Stacy E. F. Melanson

All articles by Stacy E. F. Melanson

Respiratory Alkalosis: Arterial Blood pH Increased with Decreased Arterial pCO and Decreased Arterial H2CO3-

Differential Diagnosis Hyperventilation in response to hypoxemia from a variety of causes Hyperventilation without hypoxemia as a stimulus, as in anxiety and CNS disorders that increase the respiratory rate Continue Reading Suggested Additional Lab Testing Follow arterial pH, pco2, and h2co3 as the disorder worsens or resolves.

Respiratory Acidosis: Low Arterial Blood pH with Increased Arterial pCO2 and Arterial H2CO3- Increased

Differential Diagnosis Neuromuscular disorders that decrease breathing, as produced by brain stem injury, myasthenia gravis, and poliomyelitis If sufficiently severe, multiple non-neuromuscular causes of impaired ventilation, perfusion, or gas diffusion produced by embolism, infection, selected cancers, asthma, bronchitis, and emphysema. Continue Reading Suggested Additional Lab Testing Serial blood gases to assess arterial pH, arterial pco2…

Positive Serologic Test for Hepatitis C Virus (HCV)

Differential Diagnosis Hepatitis C virus infection False-positive serologic test for hepatitis C Continue Reading Suggested Additional Lab Testing Acute hepatitis C Elevated liver function tests are expected with positive tests for anti-HCV by a variety of methods. Result may not become positive until 12-16 weeks after exposure. Patients are typically positive for HCV RNA within…

Positive Serologic Test for Hepatitis B Virus (HBV)

Differential Diagnosis Hepatitis B virus infection False-positive serologic test for hepatitis B virus Continue Reading Suggested Additional Lab Testing Acute hepatitis B Patient is positive for IgM antibody to HBV core antigen. Patient is usually positive for hepatitis B surface antigen and hepatitis B virus e antigen. Presence of the e antigen indicates a high…

Positive Serologic Test for

Differential Diagnosis Gastric ulcer Duodenal ulcer Continue Reading Suggested Additional Lab Testing For gastric ulcer: Endoscopy to visualize the ulcer; biopsy of the lesion is recommended to determine if patient has gastric adenocarcinoma. Rapid urease test of biopsy material (CLO test) verifies the presence of active infection. For duodenal ulcer disease: Urea breath test is…

Positive Screening Test for HIV

Differential Diagnosis Patient has an HIV infection. Screening test is a false-positive; there is no HIV infection. Continue Reading Suggested Additional Lab Testing Western blot Most important test for patient with a positive HIV screening test Will determine if patient has antibodies to specific HIV-associated proteins Will confirm or refute a diagnosis of HIV infection.…

Positive Anti-Nuclear Antibody (ANA) Test

Differential Diagnosis Systemic lupus erythematosus (SLE): when active, usually a homogenous pattern on ANA or less commonly speckled, rim, or nucleolar when present in high enough titer to be clinically significant Sjögren syndrome: common ANA pattern is speckled; less commonly homogenous Continue Reading Scleroderma or systemic sclerosis: ANA pattern is most commonly speckled, followed by…

Metabolic Alkalosis: Arterial Blood pH Elevated with Increased Arterial pCO2

Differential Diagnosis Vomiting or nasogastric suction Ingestion of certain drugs, such as diuretics Continue Reading Numerous endocrine disorders, including Cushing syndrome and hypoparathyroidism Suggested Additional Lab Testing Serial blood gases to assess arterial pH, arterial h2co3 and arterial pco2 are important when the disease is evolving or resolving. Tests relevant to the diagnosis of Cushing…

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