Test

Indication

Complete blood cell count

Anemia; polycythemia; vitamin B12 deficiency (hypersegmentation)

ESR

Vasculitis; tumor; infection

VDRL & FTA-ABS

Syphilis (in tertiary syphilis, serum VDRL may be negative and FTA positive)

Blood sugar

Hypo- or hyperglycemia

Blood urea nitrogen

Renal Failure

Electrolytes

Water intoxication; Adrenal disease

Calcium/Phosphorus

Hyper- or hypocalcemia; hypophosphatemia

Antinuclear antibody

Vasculitis

Protein electrophoresis

Hyperviscosity syndrome from paraproteinemia

T4/TSH

Hyper-or hypothyroidism

Cortisol

Cushing disease

Serum B12/Folate

Pernicious anemia

Ascorbate/Carotene

Malabsorption; Malnutrition

Cholesterol/triglycerides

Hyperlipidemic dementia

Liver function tests

Hepatic encephalopathy; Metastases

Arterial blood gases

Acidosis; Anoxia

Lyme titer

Lyme disease

EEG  

Slowing or triphasic waves (in most metabolic encephalopathies); focal abnormalities (such as strokes or tumors); constant seizure activity.

CT scan or MRI

Mass (neoplasm, subdural hematoma, etc), inflammatory process, stroke, hydrocephalus

Lumbar puncture: evaluation of protein, glucose, cells, culture, VDRL, fungus, electrophoresis, IgG synthesis ratio, etc.

(if not contraindicated): Inflammatory disease; infection; hydrocephalus