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32 Laboratory Medicine in Psychiatry and Behavioral Science
Aspartate transaminase (AST) (continued)
Relevance to psychiatry and AST and ALT levels may also be normal in patients with he-
behavioral science (continued) mochromatosis, in patients receiving methotrexate, or after
jejunoileal bypass surgery, despite advanced liver disease.
In all cases, the patient’s history should be central to the di
-
agnosis, and an effort should be made to identify other evi-
dence of liver disease.
Preparation of patient None needed
Indications • Component of LFT panel
• Component of CMP
• Monitoring medication effects on the liver
• Evaluating patients with clinical symptoms of liver dis-
ease, including jaundice, abdominal pain, ascites, nausea,
vomiting, or darkening of the urine (bilirubinuria)
• Distinguishing hemolytic jaundice from jaundice due to
liver dysfunction
• Evaluating patients with hepatitis exposure or symptoms
of hepatitis
• Evaluating patients with alcoholism or other substance
abuse
• Monitoring effects of treatment for liver disease
Reference range Males: 14–20 U/L
Females: 10–36 U/L
The ratio of AST to ALT is also useful in the differential diag-
nosis of the cause of liver dysfunction.
Critical value(s) >200 U/L indicates acute hepatic injury.
Increased levels • Active cirrhosis (alcohol or drug-induced)
• Hepatitis, acute or chronic
• Infectious mononucleosis
• Hepatic necrosis
• Primary or metastatic carcinoma
• Reye’s syndrome
•
MI (with AST increase paralleling that of creatine kinase)
• Numerous other conditions including hypothyroidism,
muscle trauma, muscle inflammation, toxic shock syn-
drome, cardiac catheterization, recent brain trauma,
stroke, surgery, muscular dystrophy, pulmonary embo
-
lism, malignant hyperthermia, shock, exhaustion, and
heat stroke
• Drugs metabolized in the liver, including most psycho-
tropics
Decreased levels •
Uremia in kidney failure
• Chronic dialysis
https://t.me/med1917
33 Laboratory Tests
Aspartate transaminase (AST) (continued)
Decreased levels (continued) • Vitamin B
6
(pyridoxine) deficiency
•Pregnancy
• Drugs: vitamin C, ibuprofen, naltrexone, pindolol, and
trifluoperazine
Interfering factors Diabetic ketoacidosis, severe liver disease, uremia, and sam-
ple hemolysis may give spurious results.
Cross-references Alanine Transaminase
Alcohol Use Disorder
Cirrhosis
Hepatitis, Viral
Liver Function Tests
Agrawal S, Dhiman RK, Limdi JK: Evaluation of abnormal liver function tests. Postgrad Med J
92(1086):223–234, 2016
Fischbach FT, Fischbach MA: A Manual of Laboratory and Diagnostic Tests, 10th Edition. Philadelphia,
PA, Wolters Kluwer Health/Lippincott Williams and Wilkins, 2018
Giboney PT: Mildly elevated liver transaminase levels in the asymptomatic patient. Am Fam Physician
71:1105–1110, 2005
Gopal DV, Rosen HR: Abnormal findings on liver function tests: interpreting results to narrow the diag-
nosis and establish a prognosis. Postgrad Med 107:100–114, 2000
Theal RM, Scott K: Evaluating asymptomatic patients with abnormal liver function test results. Am Fam
Physician 53:2111–2119, 1996
https://t.me/med1917
34 Laboratory Medicine in Psychiatry and Behavioral Science
Basic metabolic panel (BMP)
Type of test Blood
Background and explanation
of test
The BMP includes the following eight tests:
• Creatinine
• Glucose
• Calcium
• Sodium
• Potassium
• Carbon dioxide
• Chloride
• BUN
Relevance to psychiatry and
behavioral science
Although the BMP is often used in the emergency setting as
a means of rapidly assessing metabolic status, it is not the
panel of choice for most patients with psychiatric presenta
-
tions. In these cases, when general laboratory testing is con-
sidered necessary, the panel of choice would be the CMP,
which includes LFTs.
Preparation of patient Ideally, the patient should be fasting overnight before test-
ing, although this is rarely done. Mineral-containing supple-
ments should be held for 12 hours before testing, and
vigorous exercise should be avoided.
Indications •
Rapid workup in the emergency setting
•
Monitoring specific lab values in a hospitalized patient
Reference range See entries for individual tests.
Critical value(s) See entries for individual tests.
Increased levels See entries for individual tests.
Decreased levels See entries for individual tests.
Interfering factors See entries for individual tests.
Cross-references Comprehensive Metabolic Panel
See entries for individual tests.
https://t.me/med1917
35 Laboratory Tests
Bile acids
Type of test Blood
Background and explanation
of test
Bile acids are produced in the liver, stored in the gallbladder,
and secreted into the intestines after a meal. They facilitate
digestion by emulsifying fats and are reabsorbed with the
products of digestion. Under normal conditions, the liver is
very efficient at clearing bile acids from the blood, and serum
concentrations are low in the fasting state and increase only
slightly after meals. With liver dysfunction, however, levels
are elevated in the fasting state and may be markedly ele
-
vated after meals. Liver diseases that cause bile acid eleva-
tions include hepatitis (acute and chronic), cirrhosis, liver
cancer, cholestasis, cholangitis, portal vein thrombosis, Budd-
Chiari syndrome, Wilson’s disease, and hemochromatosis. It
is not possible to distinguish among these diseases using bile
acid testing.
Relevance to psychiatry and
behavioral science
Bile acids are a sensitive measure of liver dysfunction in cer-
tain disease states of relevance to psychiatry, as listed above.
In addition, recent evidence suggests that bile acids have a
role in mediating the effects of therapies used to treat meta
-
bolic disorders, including metformin, bile acid sequestrants,
and bariatric surgery.
Preparation of patient Patients should fast for ≥ 8 hours before the test.
Indications • Early evaluation of liver dysfunction
• Evaluating hepatic impairment from chemical and envi-
ronmental toxins
• Monitoring effects of interferon treatment for hepatitis C
• Evaluating suspected intrahepatic cholestasis of preg-
nancy
Reference range Patients 7 years of age and older:
• Total bile acids: 0–7.0 μmol/L
• Cholic acid (CA): 0–1.9 μmol/L
• Chenodeoxycholic acid (CDC): 0–3.4 μmol/L
• Deoxycholic acid (DCA): 0–2.5 μmol/L
• Ursodeoxycholic acid (UDC): 0–1.0 μmol/L
Critical value(s) None
Increased levels • Hepatitis (acute and chronic)
• Cirrhosis
• Liver cancer
• Cholestasis
• Cholangitis
• Budd-Chiari syndrome
• Wilson’s disease
https://t.me/med1917
36 Laboratory Medicine in Psychiatry and Behavioral Science
Bile acids (continued)
Increased levels (continued) • Hemochromatosis
• Intrahepatic cholestasis of pregnancy
Decreased levels Not applicable
Interfering factors Gross hemolysis or lipemia of specimen invalidates results.
Cross-references Cirrhosis
Hemochromatosis
Hepatitis, Viral
Liver Function Tests
Wilson’s Disease
ARUP Laboratories: Bile acids, total, in Lab Test Directory. Salt Lake City, UT, ARUP Laboratories, 2021.
Available at https://ltd.aruplab.com/Tests/Pub/0070189. Accessed June 2021.
Xie C, Huang W, Young RL, et al: Role of bile acids in the regulation of food intake, and their dysregula-
tion in metabolic disease.Nutrients 13(4):1104, 2021
https://t.me/med1917
37 Laboratory Tests
Bilirubin
Type of test Blood
Background and explanation
of test
When RBCs degrade, the hemoglobin component is broken
down to unconjugated (“indirect”) bilirubin. This form of
bilirubin is transformed in the liver to conjugated (“direct”)
bilirubin, which is excreted into the GI tract, where it is re
-
duced by bacteria to urobilinogen. This compound may be
excreted in feces or reabsorbed, in the latter case reappear
-
ing in urine or bile. The bilirubin cycle is shown in Appen-
dix D.
When bilirubin levels are high, patients may appear jaun-
diced. High levels may be a consequence of overproduction
(usually due to hemolysis) or underexcretion (due to liver
or biliary tract disease). Routine bilirubin measurement is of
total bilirubin; if this is not elevated, no further testing is
needed. If level is elevated, the next step is fractionation, to
determine whether bilirubin is primarily conjugated or un
-
conjugated.
When ≥30% of the bilirubin in a sample is in the conjugated
(direct) form, conjugated hyperbilirubinemia exists; the dif
-
ferential diagnosis for this condition is shown in the In-
creased Levels section below. A positive urine dipstick test for
bilirubin is also consistent with conjugated hyperbilirubin
-
emia. In addition, other LFT abnormalities are usually seen
with conjugated hyperbilirubinemia.
In general, patients with conjugated hyperbilirubinemia
should be evaluated for hepatobiliary disease, while those
with unconjugated hyperbilirubinemia should be evaluated
for causes of RBC destruction such as hemolytic anemia.
Isolated elevation of unconjugated bilirubin levels is most
often caused by Gilbert’s syndrome, a common and usually
benign genetic polymorphism associated with reduced glu
-
curonidation of bilirubin. Establishing this diagnosis avoids
costly and unnecessary testing for patients with intermit
-
tent jaundice. Any degree of bilirubinuria confirms the pres-
ence of conjugated hyperbilirubinemia, excludes hemolysis,
and indicates the presence of hepatobiliary disease.
Elevation of bilirubin may be found on routine screening. If
total bilirubin is < 1.5 times the upper limit of normal (ULN),
recheck in 1–3 months unless there is clinical suspicion of
disease. If total bilirubin is ≥1.5 times the ULN, determine
the percentage that is indirect. If >70%, the diagnosis is
probably Gilbert’s syndrome. If not, further investigation is
needed. If total bilirubin is >3 times the ULN, consultation
is indicated because clinical disease is probable.
Relevance to psychiatry and Bilirubin may be elevated in alcohol use disorder, cirrhosis,
behavioral science pernicious anemia, and cancer of the head of the pancreas
and as a drug reaction (e.g., to chlorpromazine or other phe-
nothiazines).
https://t.me/med1917
38 Laboratory Medicine in Psychiatry and Behavioral Science
Bilirubin (continued)
Preparation of patient Patients should fast for 4 hours before test and should re-
frain from eating yellow foods (e.g., carrots, yellow beans,
yams, pumpkin) for 3–4 days before test.
Indications • Component of CMP
• Presence of jaundice
• History of alcohol overconsumption
• Exposure to hepatitis
• Signs of liver injury (e.g., from drugs)
• Signs of liver disease such as cirrhosis or hepatitis
• Evidence of bile duct obstruction
• Hemolytic anemia (e.g., sickle cell disease)
Reference range Total bilirubin 0.3–1.0 mg/dL
Conjugated (direct) bilirubin 0.0–0.2 mg/dL
Critical value(s) Adults: > 12 mg/dL
Increased levels Elevation of total bilirubin
• Hepatocellular jaundice (viral hepatitis, cirrhosis, infec-
tious mononucleosis, drug reactions)
• Obstructive jaundice (gallstones, cancer)
•
Hemolytic jaundice (posttransfusion, pernicious ane-
mia, sickle cell anemia, transfusion reactions, Crigler-
Najjar syndrome)
• Gilbert’s syndrome
• Dubin-Johnson syndrome
• Pulmonary embolism
•
Congestive heart failure
Elevation of unconjugated (indirect) bilirubin
•
Hemolytic anemia due to large hematoma
• Trauma with large hematoma
• Hemorrhagic pulmonary infarcts
• Crigler-Najjar syndrome
• Gilbert’s syndrome
Elevation of conjugated (direct) bilirubin
• Blockage of liver or bile ducts
• Cancer of the head of the pancreas
• Gallstones
• Hepatitis
• Liver trauma
• Cirrhosis
https://t.me/med1917
39 Laboratory Tests
Bilirubin (continued)
Increased levels (continued) • Long-term alcohol overconsumption
• Drug reaction
• Dubin-Johnson syndrome
Decreased levels Not applicable
Interfering factors Bilirubin levels are slightly higher in males than females.
Blacks tend to have lower bilirubin values.
Strenuous exercise may increase bilirubin levels.
Fractionation tends to be unreliable in mild hyperbilirubin-
emia using standard “diazo” methods; newer, more precise
methods may be required in these cases.
Elevated bilirubin levels may be caused by alcohol, mor-
phine, theophylline, ascorbic acid, aspirin, chlordiazepox-
ide, chlorpromazine, and other phenothiazines.
Cross-references Alcohol Use Disorder
Cirrhosis
Hepatitis, Viral
Liver Function Tests
Urobilinogen
American Association for Clinical Chemistry: Testing.com. Available at: https://www.testing.com. Ac-
cessed June 2021.
Fischbach FT, Fischbach MA: A Manual of Laboratory and Diagnostic Tests, 10th Edition. Philadelphia,
PA, Wolters Kluwer Health/Lippincott Williams and Wilkins, 2018
Gopal DV, Rosen HR: Abnormal findings on liver function tests: interpreting results to narrow the diag-
nosis and establish a prognosis. Postgrad Med 107:100–114, 2000
Johnston DE: Special considerations in interpreting liver function tests. Am Fam Physician 59:2223–2230,
1999
https://t.me/med1917
40 Laboratory Medicine in Psychiatry and Behavioral Science
Blood alcohol level (BAL)
Type of test Blood
Background and explanation
of test
Alcohol is rapidly absorbed from the GI tract when it is
consumed on an empty stomach, with peak levels reached
within 1 hour of ingestion. A small amount of alcohol is
exhaled from the lungs and excreted in urine, but most is
metabolized by the liver to acetaldehyde and subsequently
to carbon dioxide and water.
A healthy liver has the capacity to metabolize about one
drink per hour (i.e., 12 oz of beer, 4–5 oz of wine, or 1–1.5 oz
of hard liquor). When more than one drink per hour is con
-
sumed, the alcohol level in the circulation rises. In the mea-
surement of the BAL, different systems of measurement
yielding different units cause some confusion as to the mean-
ings of particular values; see the Reference Range section be-
low. In general, a level equivalent to ≥0.08% is consistent
with legal intoxication in most U.S. jurisdictions.
Relevance to psychiatry and
behavioral science
Psychiatrists may be consulted for the evaluation of patients
in the emergency room who are intoxicated or withdrawing
from alcohol, and familiarity with the BAL is critical in this
context. Alcohol is also often involved in suicide attempts.
BAL may be used to monitor patients who are in treatment
for alcohol dependence.
Preparation of patient None needed
Indications • Diagnosing alcohol intoxication
• Diagnosing alcohol withdrawal
• Determining cause of coma
• Providing legal evidence in motor vehicle accident cases
or other events that may be related to intoxication
• Monitoring employees suspected of drinking on the job
• Monitoring patients who are in treatment for alcohol
dependence or abuse
• Monitoring ethanol level in patients treated for methanol
poisoning
Reference range Negative: <10 mg/dL, <2.00 mmol/L, <0.010%
Negative by U.S. Department of Transportation (DOT):
<20 mg/dL, <4.35 mmol/L, <0.020%
Positive by U.S. DOT: >40 mg/dL, >8.68 mmol/L, >0.040%
Positive under state laws: >80 mg/dL, >17.4 mmol/L,
≥0.08%
Critical value(s) • BAL >300 mg/dL is consistent with severe alcohol toxic-
ity and requires immediate treatment for overdose.
• BAL >400 mg/dL can be fatal.
https://t.me/med1917
41 Laboratory Tests
Blood alcohol level (BAL) (continued)
Critical values (continued) • Symptoms of alcohol intoxication in the presence of a
low BAL may signal a risk of serious impending with
-
drawal.
Increased levels • BAL 50–100 mg/dL: slowing of reflexes and impaired
visual acuity
• BAL >100 mg/dL: CNS depression
Decreased levels Not applicable
Interfering factors Ingestion of other alcohols (e.g., isopropanol or methanol)
can confound ethanol measurement.
Cross-references Alcohol Use Disorder
Fischbach FT, Fischbach MA: A Manual of Laboratory and Diagnostic Tests, 10th Edition. Philadelphia,
PA, Wolters Kluwer Health/Lippincott Williams and Wilkins, 2018
National Institute on Alcohol Abuse and Alcoholism: Biomarkers of heavy drinking, in Assessing Alco-
hol Problems: A Guide for Clinicians and Researchers. Edited by Allen JP, Wilson VB. Available at:
https://pubs.niaaa.nih.gov/publications/assessingalcohol/allen.pdf
. Accessed June 2021.
https://t.me/med1917
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