Test
Specimen
Normal range
WBC count
Blood
3.9–10.7 × 103 cells/μL
Hemoglobin
Blood
12–17 g/dL
Hematocrit
Blood
36–51 %
Platelet count
Blood
150–350 × 103/μL
Sodium
Blood/serum
136–145 mEq/L
Potassium
Blood/serum
3.5–5 mEq/L
Chloride
Blood/serum
98–106 mEq/L
Bicarbonate (CO2)
Blood/serum
23–28 mEq/L
BUN
Blood/ serum
8–20 mg/dL
Creatinine
Blood/serum
0.7–1.3 mg/dL
Glucose (fasting)
Blood/serum
70–105 mg/dL
Urinalysis (UA) : If there is suspicion of urinary tract infection (UTI), e.g., dysuria, frequency, or urgency, with a normal UA, a urine culture should be ordered. UTIs are a common cause of mental status change in the elderly (see TIPS below).
The below values are usually absent or negative with a normal UA:
- a.
Protein: usually absent; present in renal disease
- b.
Leukocyte esterase (released from leukocytes): present in UTI and/or inflammation of the urinary tract
- c.
Glucose: present in diabetes mellitus (DM), pancreatic disorders, liver disease, drugs (steroids, diuretics).
- d.
Nitrite (produced by certain bacteria): present in UTI
- e.
Bilirubin: present in liver and biliary tract disease
- f.
RBCs: present in renal disease, UTI, urinary tumor, urolithiasis
- g.
Ketones: present in uncontrolled DM, starvation, vomiting/diarrhea, alcoholics
- h.
Specific Gravity (SG): nml range 1.00–1.03; elevated SG may indicate dehydration, SIADH
Secondary Blood Tests
Should be considered if the history (e.g., alcohol abuse), signs/symptoms (e.g., jaundice, hallucinations), or basic labs (e.g., elevated transaminases) warrant further investigation into the cause of acute or chronic mental status change.
- 1.
Cerebral Spinal Fluid (CSF)
Obtained through lumbar puncture; contraindicated if coagulopathy is present (e.g., on Coumadin, presence of liver disease) or in the presence of papilledema.
- a.
Opening pressures: increased in meningitis, tumors; normal in multiple sclerosis (MS).
- b.
Protein (IgG antibodies): increased in encephalitis, meningitis, MS, cerebral abscess/tumor, post-infectious polyneuropathy (e.g., AIDP/CIDP), Intracranial Hemorrhage (ICH) and stroke due to increased permeability at the blood–brain barrier.
- c.
WBC count : increased in bacterial and viral meningitis, MS.
- d.
RBC count: increased in ICH.
- e.
Glucose: decreased in bacterial, fungal, or TB meningitis.
- a.
- 2.
Toxicology Panel : Blood and Urine Drug Screen (UDS) [3]
Most toxicology panels are fairly extensive, and include dozens of analytes such as salicylates, alcohol, amphetamines, barbiturate, acetaminophen, iron, lead, THC, carbon monoxide, ethylene glycol, benzodiazepines, morphine or other opioids, PCP, tricyclic antidepressants. Adding prescription medications may be indicated.
- 3.
Liver function tests (LFTs) : Serum ALT and AST are elevated in liver disease, exercise, myopathy, medication (e.g., acetaminophen, antibiotics, several diabetic and cardiovascular meds, valproate, tizanidine); 10× normal indicates severe hepatic disease. Gamma glutamyl transpeptidase (GGT) is often added to rule out bone pathology and to help confirm liver disease.
- 4.
Ammonia (NH3) : Increased in liver disease, sepsis, GI bleed, medication (valproate), genetic metabolic disease.Related posts:
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