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72 Laboratory Medicine in Psychiatry and Behavioral Science
Chest X-ray (CXR) (continued)
Interfering factors (continued) If patients are unable to travel to the radiology department,
an anterior-to-posterior film is obtained in bed, in the up
-
right position. This view is much less likely to reveal pathol-
ogy, particularly in area blocked by heart.
Cross-references Delirium
Tuberculosis
Fauci AS, Braunwald E, Kasper DL, et al (eds): Harrison’s Principles of Internal Medicine, 17th Edition.
New York, McGraw-Hill, 2008
Jacobi A, Chung M, Bernheim A, Eber C: Portable chest X-ray in coronavirus disease-19 (COVID-19): a
pictorial review. Clin Imaging 64:35–42, 2020
https://t.me/med1917
73 Laboratory Tests
Chlordiazepoxide level
Type of test Blood
Background and explanation
of test
Benzodiazepines are Schedule IV sedative-hypnotic drugs
used to treat anxiety and insomnia. Chlordiazepoxide (Lib
-
rium and others) is a benzodiazepine that is also commonly
used to treat alcohol withdrawal. It is an intermediate-acting
drug with a long half-life and with active metabolites. In
general, levels of the parent drug and its metabolite nordiaz-
epam are checked either when overdose or noncompliance
is suspected or to detect use without a prescription. In the
latter case, a urine drug screen would more likely be used to
detect the metabolite oxazepam.
Relevance to psychiatry and
behavioral science
Toxicity with chronic benzodiazepine ingestion may mani-
fest as confusion, disorientation, memory impairment,
ataxia, decreased reflexes, and dysarthria. With acute over
-
dose, the patient may exhibit somnolence, confusion, ataxia,
decreased reflexes, vertigo, dysarthria, respiratory depres-
sion, and coma. More serious consequences usually involve
co-ingestion of alcohol or other sedatives. The administra
-
tion of flumazenil does not affect the drug level.
Preparation of patient None needed
Indications •
Screening for drug use
•
Suspicion of overdose
• Signs of toxicity in a treated patient
• Suspected noncompliance with prescribed therapy
Reference range Chlordiazepoxide 500–3,000 ng/mL
Nordiazepam 100–1,500 ng/mL
Critical value(s) Chlordiazepoxide >5,000 ng/mL
Nordiazepam >2,500 ng/mL
Increased levels • Overdose
• Overuse
• Poor metabolism
• Hepatic encephalopathy
Decreased levels Noncompliance
Interfering factors None
Cross-references Benzodiazepines
Urine Drug Screen
ARUP Laboratories: Benzodiazepines, urine, quantitative, in Lab Test Directory. Salt Lake City, UT, ARUP
Laboratories, 2021. Available at: https://ltd.aruplab.com/Tests/Pub/2008291. Accessed June 2021.
Galanter M, Kleber HD (eds): The American Psychiatric Publishing Textbook of Substance Abuse Treat-
ment, 4th Edition. Washington, DC, American Psychiatric Publishing, 2008
Wu AHB: Tietz Clinical Guide to Laboratory Tests, 4th Edition. St. Louis, MO, WB Saunders, 2006
https://t.me/med1917
74 Laboratory Medicine in Psychiatry and Behavioral Science
Chloride
Type of test Blood
Background and explanation
of test
Chloride is an anion found in high concentration in the ex-
tracellular fluid, where it works to maintain osmotic pres-
sure and water balance and acts as a buffer to maintain acid-
base balance. Usually, chloride concentration rises and falls
with sodium, but the chloride level can change indepen
-
dently when an acid-base imbalance occurs as the ion
moves into and out of cells to maintain electrical neutrality.
Chloride is ingested in food and table salt, with most ab-
sorbed in the GI tract and the excess excreted in urine. Nor-
mal blood levels are stable, with a slight decrease after
meals, when the stomach produces acid to aid digestion us
-
ing chloride from blood. When a massive diuresis occurs
(e.g., with diabetes insipidus), chloride is lost through the
urinary system. With significant vomiting or diarrhea, chlo
-
ride is lost directly from the GI tract.
Chloride is measured as a routine component of electrolyte
panels because it is useful in the diagnosis of acid-base and
water balance problems. The results of the blood test may
be followed up with a blood gas, urine chloride testing, or
blood or urine sodium measurement.
Relevance to psychiatry and
behavioral science
Chloride levels are affected by any process that involves loss
of fluid from the GI tract, changes in acid-base balance, or
changes in sodium concentration. Neuropsychiatric condi
-
tions that may be associated with chloride derangements in-
clude diabetes insipidus, lithium intoxication, SIAD,
psychogenic polydipsia, porphyria, TBI, eating disorders
with purging behaviors, and hyperventilation.
Preparation of patient Patient should fast for ≥ 8 hours before testing.
Indications •
Routine component of blood panels (electrolyte panel,
BMP, CMP)
• Suspicion of acidosis or alkalosis
• Respiratory distress
• Prolonged vomiting or diarrhea
• Massive diuresis
Reference range 96–106 mEq/L
Values
may be higher in patients > 90 years.
Critical value(s) < 70 mEq/L or >120 mEq/L
Increased levels •
Dehydration
• Cushing’s syndrome (with high sodium level)
• Metabolic acidosis (with prolonged diarrhea)
• Respiratory alkalosis (with hyperventilation)
• Primary hyperparathyroidism
https://t.me/med1917
75 Laboratory Tests
Chloride (continued)
Increased levels (continued) • Certain kidney diseases (e.g., renal tubular acidosis)
• Diabetes insipidus
• Salicylate intoxication
• TBI with hypothalamic injury
• Eclampsia
Decreased levels • Prolonged vomiting
• Gastric suction
• Salt-wasting diseases (e.g., SIAD, nephritis)
• Chronic respiratory acidosis
• Burns
• Metabolic alkalosis
• Overhydration or water intoxication
• Addison’s disease
• Congestive heart failure
• Acute intermittent porphyria
Interfering factors Medications containing bromide can produce a positive re-
action with some ion-selective electrode assays for chloride.
Drugs that affect sodium level also affect chloride level.
Ingestion of large amounts of baking soda or antacids can
lower chloride level.
Excessive IV saline infusion causes elevated chloride level.
Cross-references Bulimia Nervosa
Diabetes Insipidus
Lithium
Porphyria
Psychogenic Polydipsia
Syndrome of Inappropriate Antidiuresis
Ahmadi L, Goldman MB: Primary polydipsia: update.Best Pract Res Clin Endocrinol Metab
34(5):101469, 2020
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
Germon K: Fluid and electrolyte problems associated with diabetes insipidus and syndrome of inappro-
priate antidiuretic hormone. Nurs Clin North Am 22:785–796, 1987
Sailer C, Winzeler B, Christ-Crain M: Primary polydipsia in the medical and psychiatric patient: charac-
teristics, complications and therapy. Swiss Med Wkly 147:w14514, 2017
Siragy HM: Hyponatremia, fluid-electrolyte disorders, and the syndrome of inappropriate antidiuretic
hormone secretion: diagnosis and treatment options. Endocr Pract 12:446–457, 2006
https://t.me/med1917
76 Laboratory Medicine in Psychiatry and Behavioral Science
Cholinesterase
Type of test Blood
Background and explanation
of test
Cholinesterase levels are used to confirm organophosphate
poisoning. Organophosphate compounds are found in in
-
secticides (e.g., malathion and parathion) and nerve gases
(e.g., soman and sarin). These compounds inhibit the
enzyme acetylcholinesterase, which breaks down acetyl
-
choline. Symptoms of toxicity are attributable to cholinergic
excess. Exposure can occur by inhalation, ingestion, or skin
contact. Those at risk of exposure include farmworkers, gar
-
deners, manufacturers, fumigators, military personnel, and
children.
Both RBC cholinesterase and plasma cholinesterase assays
are available. RBC cholinesterase is more accurate, but
plasma cholinesterase is easier to perform and more readily
available. Blood should be drawn before treatment com
-
mences, but treatment should not wait until results are
returned. Cholinesterase levels do not always correlate
with severity of clinical symptoms.
Relevance to psychiatry and
behavioral science
Initial psychiatric symptoms of acute organophosphate
exposure include anxiety and emotional lability, poor con
-
centration, insomnia, and nightmares. With more serious
exposure, apathy, depression, anorexia, decreased libido,
restlessness, hyperactivity, suicidal ideation, confusion,
memory problems, hallucinations, paranoid ideation, and
dissociation may be seen. Motor symptoms include tremor,
ataxia, and seizures. Many of the same symptoms can be
seen with chronic exposure. Genetic susceptibility has been
described and can account for toxicity with relatively low-
level exposure in some cases.
Preparation of patient None needed
Indications Clinical suspicion of organophosphate poisoning
Reference range Plasma cholinesterase: 2.9–7.1 U/mL
RBC cholinesterase: 7.9–17.1
U/mL
RBC cholinesterase-to-hemoglobin ratio: 25–52 U/g
hemoglobin
Critical value(s) None
Increased levels Acute or chronic organophosphate exposure
Decreased levels Not applicable
Interfering factors Spuriously reduced RBC cholinesterase levels may be found
in patients with pernicious anemia or hemoglobinopathies
and in those taking antimalarial drugs.
Spuriously reduced plasma cholinesterase may be found in
patients with liver disease, pregnancy, hypoproteinemia,
neoplasia, hypersensitivities, or certain genetic deficiency
syndromes and in those taking specific drugs (e.g., mor-
phine, codeine, succinylcholine).
https://t.me/med1917
77 Laboratory Tests
Cholinesterase (continued)
Interfering factors (continued) Specimen handling: Frozen, clotted, or hemolyzed specimens
invalidate results; use of oxalate blood tubes invalidates re
-
sults.
Cross-references Organophosphate Poisoning
ARUP Laboratories: Cholinesterase, RBC: ratio to hemoglobin, in Lab Test Directory. Salt Lake City, UT,
ARUP Laboratories, 2021. Available at: https://ltd.aruplab.com/Tests/Pub/0020174. Accessed June
2021.
Brown JS: Environmental and Chemical Toxins and Psychiatric Illness. Washington, DC, American Psy-
chiatric Publishing, 2002
Katz KD, Brooks DE: Organophosphate toxicity clinical presentation. Medscape, December 31, 2020.
Available at: https://emedicine.medscape.com/article/167726-clinical. Accessed June 2021.
https://t.me/med1917
78 Laboratory Medicine in Psychiatry and Behavioral Science
Clonazepam level
Type of test Blood
Background and explanation
of test
Clonazepam (Klonopin, Rivotril) is a member of the class of
drugs known as benzodiazepines, which are Schedule IV
sedative-hypnotics used to treat anxiety and insomnia. In
general, benzodiazepine levels are checked when either
overdose or noncompliance is suspected or to detect use
without a prescription. For the latter indication, a urine
drug screen would more likely be used than a blood level.
Relevance to psychiatry and
behavioral science
Toxicity with chronic benzodiazepine ingestion may mani-
fest as confusion, disorientation, memory impairment,
ataxia, decreased reflexes, and dysarthria. There is some ev
-
idence that use of long-acting benzodiazepines such as
clonazepam is associated with an increased risk of motor
vehicle accidents and falls in elderly patients, even when
levels are within the therapeutic range. With acute benzo
-
diazepine overdose, patients may exhibit somnolence,
confusion, ataxia, decreased reflexes, vertigo, dysarthria,
respiratory depression, and coma. More serious conse
-
quences usually involve co-ingestion of alcohol or other
sedatives. Administration of flumazenil does not affect the
drug level.
Preparation of patient None needed
Indications • Suspected noncompliance with prescribed therapy
• Screening for drug use
• Suspicion of overdose
• Signs of toxicity in a treated patient
Reference range 20–70 ng/mL (for dosages of 1–8 mg/day)
Critical value(s) >80 ng/mL
Increased levels • Overdose
• Overuse
• Poor metabolism
• Hepatic encephalopathy
Decreased levels Noncompliance
Interfering factors None
Cross-references Benzodiazepines
Urine Drug Screen
ARUP Laboratories: Clonazepam, in Lab Test Directory. Salt Lake City, UT, ARUP Laboratories, 2021.
Available at: https://ltd.aruplab.com/Tests/Pub/0090055. Accessed June 2021.
Chernecky CC, Berger BJ: Laboratory Tests and Diagnostic Procedures, 5th Edition. St. Louis, MO, WB
Saunders, 2008
Wu AHB: Tietz Clinical Guide to Laboratory Tests, 4th Edition. St. Louis, MO, WB Saunders, 2006
https://t.me/med1917
79 Laboratory Tests
Clozapine level
Type of test Blood
Background and explanation
of test
Clozapine (Clozaril and others) is an atypical antipsychotic
drug used to treat patients with schizophrenia and related
illnesses who have had a poor response to other drugs, par
-
ticularly patients with recurrent suicidal ideation. The
threshold level for clinical response is generally taken as 350
ng/mL. The dose-concentration relationship is affected by
several variables, including ethnicity; Asian individuals re
-
quire only 50% of the usual dosage to achieve the target level.
Relevance to psychiatry and
behavioral science
Clozapine is the prototype atypical antipsychotic drug—the
first to be marketed and still widely considered the most
efficacious. Use of clozapine is limited by its potential to
cause severe neutropenia and other serious adverse effects.
In addition to schizophrenia, clozapine is used in the treat-
ment of schizoaffective disorder, bipolar disorder, Parkin-
son’s disease with psychosis, dementia with Lewy bodies,
and psychosis in patients with tardive dyskinesia. Cloza
-
pine blood levels are routinely monitored during treatment
and should also be checked when interacting drugs are
started or discontinued and in the event of infection, which
can be associated with increased clozapine levels.
Preparation of patient Blood should be drawn at steady state (5–7 days after the
last change in dosage), 12±2 hours after the last dose.
Indications •
Clozapine dosage >600 mg/day* (higher risk of sei-
zures)
• Signs/symptoms of toxicity
• Expected drug interactions when other medications are
used
• Suspected noncompliance
• Poor response to treatment
Reference range 350–600 ng/mL for major psychiatric disorders such as
schizophrenia
For psychosis arising in the context of medical conditions
and for elderly patients, lower drug levels may be appropri
-
ate. Some patients with treatment-refractory schizophrenia
benefit from higher drug levels.
Critical value(s) ≥ 1,000 ng/mL
Increased levels Toxicity
Decreased levels Influenced by many variables, including noncompliance
with treatment. See Clozapine in the Psychotropic Medica
-
tions chapter for more information.
Interfering factors None
Cross-references Clozapine
Therapeutic and Toxic Drug Levels at a Glance
(Appendix A)
*A lower threshold would apply to Asian patients.
https://t.me/med1917
80 Laboratory Medicine in Psychiatry and Behavioral Science
Clozapine level (continued)
American Society of Health-System Pharmacists: AHFS Drug Information. Bethesda, MD, American So-
ciety of Health-System Pharmacists, 2016
Clark SR, Warren NS, Kim G, et al: Elevated clozapine levels associated with infection: a systematic re-
view. Schizophr Res 192:50–56, 2018
de Leo n J, Ruan CJ, Sc hore tsanitis G , De Las Cuevas C: A rational use of clozapine based on adverse drug
reactions, pharmacokinetics, and clinical pharmacopsychology. Psychother Psychosom 89(4):200–
214, 2020
de Leon J, Schoretsanitis G, Kane JM, Ruan CJ: Using therapeutic drug monitoring to personalize cloza-
pine dosing in Asians.Asia Pac Psychiatry 12(2):e12384, 2020
https://t.me/med1917
81 Laboratory Tests
Complete blood count (CBC)
Type of test Blood
Background and explanation
of test
The CBC is an automated count of blood cells that reports
the following information: WBC, RBC, and platelet counts
per volume, platelet volume, hemoglobin content, hemato
-
crit, and red cell indices (MCV, mean corpuscular hemoglo-
bin [MCH], mean corpuscular hemoglobin concentration
[MCHC], and red cell distribution of width [RDW]).
MCH is a calculation of the amount of oxygen-carrying he-
moglobin in a single RBC. Macrocytic RBCs have higher
MCH values, and microcytic RBCs have lower MCH values.
MCHC is a calculation of the average concentration of he-
moglobin in RBCs. Low MCHC, or hypochromia, is seen
with diseases such as iron deficiency anemia or thalassemia,
in which hemoglobin is diluted. High MCHC, or hyperchro
-
mia, is seen with conditions such as burns, in which hemo-
globin is concentrated.
RDW is a calculation of the variance in size (anisocytosis)
and shape (poikilocytosis) of RBCs.
If a differential
is ordered with the CBC, types of WBCs are
identified either manually
or by automated means.
For any of the blood cells, unusual cell types or morpholo-
gies are explored through examination of a blood smear and
are reported with the routine CBC. Other components of the
CBC are discussed in separate entries in this chapter.
Relevance to psychiatry and This is a basic screening test that aids in the diagnosis of nu-
behavioral science merous medical conditions that can cause symptoms resem-
bling primary psychiatric diseases. The CBC is a high-yield,
low-cost test.
Preparation of patient Fasting is not required. Physiological stress should be
avoided just prior to testing.
Indications •
Basic screening panel for hospital admission and general
health status
• Presurgical evaluation
• Monitoring after surgery
• Clinical signs/symptoms such as fever, fatigue, weak-
ness, or abnormal bleeding or bruising
• Clinical suspicion of infection or inflammation
Reference range MCH: 28–34 pg/cell
MCHC: 32–36 g/dL
RDW: 11.5%–14.5%
For all other values, see individual test components.
Critical value(s) See entries for test components.
Increased levels See entries for test components.
Decreased levels See entries for test components.
https://t.me/med1917
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