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292 Laboratory Medicine in Psychiatry and Behavioral Science
Urine microalbumin (continued)
Increased levels • Diabetes
• Hypertension
• CNS infection
• SLE
• Kidney disease (glomerular or tubular)
• Urinary tract infection
• Congestive heart failure
• Leukemia, lymphoma, multiple myeloma
• Wilson’s disease
• Sickle cell disease
• Acute infection, sepsis
• Trauma
• Hyperthyroidism
• Vascular disease
• Poisoning (turpentine, phosphorus, mercury, gold, lead,
phenol, opiates, other drugs)
Decreased levels Not applicable
Interfering factors Strenuous exercise, fever, exposure to cold, dehydration,
contrast dye within 3 days of testing, pregnancy
Cross-references Creatinine
Urine Protein
American Association for Clinical Chemistry: Testing.com. Available at: https://www.testing.com. Ac-
cessed October 2021.
Fischbach FT, Fischbach MA: A Manual of Laboratory and Diagnostic Tests, 10th Edition. Philadelphia,
PA, Wolters Kluwer Health/Lippincott Williams and Wilkins, 2018
Lessey G, Stavropoulos K, Papademetriou V: Mild to moderate chronic kidney disease and cardiovascu-
lar events in patients with type 2 diabetes mellitus. Vasc Health Risk Manag 15:365–373, 2019
Márquez DF, Ruiz-Hurtado G, Segura J, Ruilope L: Microalbuminuria and cardiorenal risk: old and new
evidence in different populations.F1000Res 8:F1000 Faculty Rev-1659, 2019
Weir MR: Microalbuminuria and cardiovascular disease.Clin J Am Soc Nephrol 2(3):581–590, 2007
https://t.me/med1917
293 Laboratory Tests
Urine nitrite
Type of test Component of routine urinalysis
Background and explanation
of test
Nitrates normally present in urine can be converted to ni-
trites by certain gram-negative bacteria, causing a positive
dipstick test that may indicate a urinary tract infection
(UTI). A positive nitrite test is followed up by microscopic
examination of the urine and, in some cases, by a urine cul-
ture. The latter is the gold standard for UTI diagnosis but is
expensive and takes time to report. Because not all bacteria
implicated in a UTI are capable of reducing nitrate, nitrite
testing alone could produce a false-negative result. Nitrite
results are therefore considered along with findings from
the leukocyte esterase dipstick, microscopic examination for
WBCs, and clinical signs and symptoms suggestive of a UTI.
Relevance to psychiatry and
behavioral science
Testing for nitrite is helpful in the detection of a UTI, which
can be associated with delirium and other mental status
changes, particularly in elderly patients.
Preparation of patient See Urinalysis. If a random sample is used, it should be col-
lected ≥4 hours after the last voiding to ensure the adequate
contact time between bacteria and nitrates.
Indications • Component of routine urinalysis
•
Screening populations at risk of UTI: pregnant females,
patients with diabetes, elderly patients, school-age chil-
dren (particularly female), patients with recurrent UTI
history
• Monitoring treatment for UTI
Reference range Negative on dipstick
Microscopic exam: <10
3
bacteria/mL or ≤20 bacteria/hpf
Critical value(s) None
Positive test Significant bacteriuria present; perform urine culture.
Negative test Does not necessarily signify absence of UTI, for the follow-
ing reasons:
• Infection is caused by bacteria that do not convert ni-
trate to nitrite (e.g., staphylococcus, streptococcus)
• Urine is not present in bladder long enough for nitrate-
to-nitrite conversion
• Insufficient amounts of nitrate present in patient diet
Interfering factors False-negative results can occur with high urine output, di-
abetes mellitus, SLE, sickle cell anemia, agammaglobulin-
emia, localized infection, use of certain drugs (antibiotics,
anti-inflammatory drugs, high-dose vitamin C), or storage
of dipsticks in a humid environment.
False-positive results can occur with use of certain drugs
(e.g., oral contraceptives or phenazopyridine).
Improper specimen handling (e.g., delay in processing or
failure to refrigerate) can invalidate the results.
https://t.me/med1917
294 Laboratory Medicine in Psychiatry and Behavioral Science
Cross-references Urinalysis
Urinary Tract Infection
Urine nitrite (continued)
American Association for Clinical Chemistry: Testing.com. Available at: https://www.testing.com. Ac-
cessed October 2021.
Chu CM, Lowder JL: Diagnosis and treatment of urinary tract infectionsacross age groups.Am J Obstet
Gynecol 219(1):40–51, 2018
Fischbach FT, Fischbach MA: A Manual of Laboratory and Diagnostic Tests, 10th Edition. Philadelphia,
PA, Wolters Kluwer Health/Lippincott Williams and Wilkins, 2018
Giesen LG, Cousins G, Dimitrov BD, et al: Predicting acute uncomplicated urinary tract infection in
women: a systematic review of the diagnostic accuracy of symptoms and signs.BMC Fam Pract 11:78,
2010
Masajtis-Zagajewska A, Nowicki M: New markers of urinary tract infection. Clin Chim Acta 471:286–
291, 2017
https://t.me/med1917
295 Laboratory Tests
Urine pH
Type of test Component of routine urinalysis
Background and explanation
of test
Urine is typically slightly acidic, with a pH of ~6.0 and a nor-
mal range from 4.5 to 8 . Diet and drugs both affect urine pH,
as does any condition causing systemic acidosis or alkalosis.
Urine pH can be manipula ted in the management of kidney
stones, which precipitate differently at particular pH values.
Stones that precipitate in acidic urine include uric acid, cal-
cium oxalate, cystine, and xanthine stones.
Stones that precipitate in alkaline urine include calcium
phosphate, calcium carbonate, and magnesium phosphate
stones.
Urine pH can also be adjusted to make medications such as
streptomycin, neomycin, and kanamycin more effective in
treating UTI because these drugs are more active in alkaline
urine.
Relevance to psychiatry and
behavioral science
See Acidic Urine and Alkaline Urine sections below.
Preparation of patient See Urinalysis.
Indications Component of routine urinalysis
Reference range 4.5–8.0 (average 6.0)
Critical value(s) None
Acidic urine (pH <7.0) • Fever
• Metabolic acidosis
• Diabetic ketosis
• Diarrhea
• Starvation
• Uremia
• Urinary tract infection (e.g., Escherichia coli)
• Respiratory acidosis
• Renal tuberculosis
Alkaline urine (pH >7.0) • Urinary tract infection (e.g., Proteus, Pseudomonas)
• Renal tubular acidosis
• Chronic renal failure
• Vomiting or gastric suctioning
• Hyperventilation with respiratory alkalosis
Interfering factors Urine allowed to stand before analysis becomes more alka-
line. If urine pH
is >9, another specimen is required.
Urine becomes alkaline after eating and becomes acidic af-
ter overnight fasting.
Urine becomes alkaline with diets high in citrus fruits, veg-
etables, and dairy products.
https://t.me/med1917
296 Laboratory Medicine in Psychiatry and Behavioral Science
Urine pH (continued)
Interfering factors (continued) Urine becomes acidic with diets high in meat products and
cranberries.
Specific medications can change urine pH:
• Drugs that produce alkaline urine (high pH) include
acetazolamide, potassium citrate, and sodium bicar-
bonate.
• Drugs that produce acidic urine (low pH) include am-
monium chloride, thiazide diuretics, and methenamine
mandelate.
Cross-references Urinalysis
Urinary Tract Infection
American Association for Clinical Chemistry: Lab Tests Online. Available at: https://www.testing.com.
Accessed October 2021.
Fischbach FT, Fischbach MA: A Manual of Laboratory and Diagnostic Tests, 10th Edition. Philadelphia,
PA, Wolters Kluwer Health/Lippincott Williams and Wilkins, 2018
Simerville JA, Maxted WC, Pahira JJ: Urinalysis: a comprehensive review. Am Fam Physician 71:1153–
1162, 2005
https://t.me/med1917
297 Laboratory Tests
Urine protein
Type of test Component of routine urinalysis
Background and explanation
of test
The transient appearance of protein in the urine can occur
with urinary tract infection, fever, stress, strenuous exercise,
exposure to cold, or contamination with vaginal mucus. In
addition, orthostatic proteinuria can be identified in patients
younger than 30 years when urine that is sampled after the
patient has been in the upright position shows significant
protein, whereas urine sampled after the patient has been in
the supine position does not. From the standpoint of the kid
-
ney, these findings are considered benign.
The persistence of anything more than trace proteinuria, on
the other hand, can be a critical and early indicator of renal
dysfunction. This type of proteinuria may be a consequence
of primary renal disease or renal dysfunction secondary to
conditions such as diabetes, vasculitis, amyloidosis, connec
-
tive tissue disease, myeloma, congestive heart failure (CHF),
or hypertension.
Qualitative urine protein testing is usually performed by
dipstick, which primarily detects albumin. Follow-up could
involve either a spot urine to determine the protein-to
-
creatinine ratio or a 24-hour urine collection.
Relevance to psychiatry and
behavioral science
Among many other conditions, persistent proteinuria may
signal the presence of a disease such as vasculitis or CHF,
which could present with psychiatric symptoms.
Preparation of patient See Urinalysis.
Indications Component of routine urinalysis
Reference range Normal total protein excretion:
• ≤ 10 mg/100 mL in a single specimen (a negative result)
• ≤ 150 mg/24 hours (≤ 15 mg/dL)
Some
labs report semiquantitative test results for spot urine,
interpreted as follows:
• Trace: equivalent to 150 mg/24 hours
• 1+: 200–500 mg/24 hours
• 2+: 500–1,500 mg/24 hours
• 3+: 2,000–5,000 mg/24 hours
• 4+: 7,000 mg/24 hours
Critical value(s) > 150 mg/24 hours defines proteinuria (1+ to 4+).
>2,000 mg/24 hours in adults usually indicates glomerular
etiology.
>3,500 mg/24 hours is consistent with nephrotic syndrome
(with hypoalbuminemia, edema, and hyperlipidemia).
https://t.me/med1917
298 Laboratory Medicine in Psychiatry and Behavioral Science
Urine protein (continued)
Increased levels • Glomerular injury: glomerulonephritis, SLE, malignant
hypertension, nephrotic syndrome, amyloidosis, and
diabetes mellitus
• Renal tubular dysfunction: pyelonephritis, Wilson’s
disease, and interstitial nephritis
• Extrarenal causes: COVID-19 infection, CHF, increased
serum proteins (multiple myeloma, lymphoma), sepsis,
trauma, hyperthyroidism, cardiovascular disease, CNS
lesions, renal transplant rejection, and poisoning by var-
ious substances (e.g., turpentine, opioids)
• Proteinuria with increased WBCs: urinary tract infection
• Proteinuria with increased WBCs and RBCs: inflamma-
tion of glomeruli (pyelonephritis)
Decreased levels Not applicable
Interfering factors Transient proteinuria is seen with the following conditions:
strenuous exercise, seizures, emotional stress, cold expo
-
sure, fever, dehydration, certain food allergies, use of salic-
ylates, premenstrual state, post-labor and delivery.
False-positive urine protein is seen with alkaline urine,
blood, vaginal discharge, and semen.
False-negative urine protein is seen with very dilute urine.
Because the dipstick primarily detects albumin, it would not
detect abnormal proteins, such as Bence Jones proteins.
Some renal diseases are not associated with proteinuria.
Cross-references Systemic Lupus Erythematosus
Thyrotoxicosis
Urinalysis
Urine Microalbumin
Wilson’s Disease
American Association for Clinical Chemistry: Testing.com. Available at: https://www.testing.com. Ac-
cessed October 2021.
George JA, Khoza S: SARS-CoV-2 infection and the kidneys: an evolving picture.Adv Exp Med Biol
1327:107–118, 2021
Haynes J, Haynes R: Proteinuria. BMJ 332(7536):284, 2006
Polkinghorne KR: Detection and measurement of urinary protein.Curr Opin Nephrol Hypertens
15(6):625–630, 2006
https://t.me/med1917
299 Laboratory Tests
Urine red blood cells (RBCs) and RBC casts
Type of test Component of routine urinalysis
Background and explanation
of test
The presence of intact RBCs in the urine is termed hematuria,
which is categorized as gross (visible to the naked eye) or
microscopic (seen on microscopic urinalysis). The differential
diagnosis for hematuria ranges from transient and benign
etiologies to persistent and serious causes, such as urothelial
carcinoma, as noted below. Urine dipstick testing is highly
sensitive to
hematuria but cannot distinguish intact RBCs
from
myoglobin or free hemoglobin, so a positive dipstick
test must be followed by microscopic examination of the
urine.
Initial findings on urinalysis can help distinguish glomeru-
lar from non-glomerular causes of hematuria. A glomerular
cause (arising from the kidney itself) is suggested by the
presence of dysmorphic RBCs, significant proteinuria, and
RBC casts and should prompt referral to a nephrologist.
The risk of urothelial carcinoma increases with the number
of RBCs found on high-power microscopy as well as older
age, positive smoking history, and male sex.
Relevance to psychiatry and
behavioral science
Behavioral health specialists are cautioned not to ignore
urine blood. An initial separation of findings into glomeru
-
lar versus non-glomerular origin can facilitate appropriate
patient referral.
Preparation of patient See Urinalysis.
Indications Component of routine urinalysis
Reference range RBCs: 0–3/hpf (40× magnification)
RBC casts: 0/lpf (20× magnification)
Critical value(s) Hematuria is defined as >3 RBCs/hpf.
Presence of RBC casts indicates glomerular injury or, less
commonly, severe tubular damage, among other conditions
(e.g., congestive heart failure, malignant hypertension, lu-
pus nephritis, acute bacterial endocarditis).
Abnormal test Hematuria without other cells, casts, or protein suggests
bleeding from the urinary tract. Common causes of isolated
hematuria include stones, neoplasms, tuberculosis, trauma,
and prostatitis. Blood clots with gross bleeding point to the
urinary collecting system. WBCs present along with RBCs
suggest the presence of infection.
Decreased levels Not applicable
Interfering factors A single urine specimen with hematuria can be found with
menstruation, sexual intercourse, strenuous exercise, mild
trauma, dehydration, allergy, or viral illness.
Heavy smokers often have small numbers of RBCs in urine.
Drugs associated with urine RBCs include aspirin, NSAIDs,
heparin, amitriptyline, chlorpromazine, anticonvulsants,
oral contraceptives, penicillin, and cyclophosphamide.
https://t.me/med1917
300 Laboratory Medicine in Psychiatry and Behavioral Science
Urine red blood cells (RBCs) and RBC casts (continued)
Cross-references Urinalysis
Urinary Tract Infection
Urine Blood, Hemoglobin, and Myoglobin
Barocas DA, Boorjian SA, Alvarez RD, et al: Microhematuria: AUA/SUFU guideline. J Urol 204:778, 2020
Becker GJ, Garigali G, Fogazzi GB: Advances in urine microscopy.Am J Kidney Dis 67(6):954–964, 2016
Fischbach FT, Fischbach MA: A Manual of Laboratory and Diagnostic Tests, 10th Edition. Philadelphia,
PA, Wolters Kluwer Health/Lippincott Williams and Wilkins, 2018
Sharp VJ, Barnes KT, Erickson BA: Assessment of asymptomatic microscopic hematuria in adults.Am
Fam Physician 88(11):747–754, 2013
https://t.me/med1917
301 Laboratory Tests
Urine specific gravity
Type of test Component of routine urinalysis
Background and explanation
of test
Urine specific gravity (SG) is a measure of the density of
urine, reflecting the kidney’s ability to produce a concen
-
trated or dilute urine in relation to plasma. It is proportional
to urine osmolality. It can be performed by dipstick or in the
laboratory.
Relevance to psychiatry and
behavioral science
Urine SG can be a quick and readily available gauge of de-
hydration, overhydration (as with polydipsia), or urine os-
molality.
Preparation of patient See Urinalysis.
Indications Component of routine urinalysis
Reference range Normal kidney: 1.002–1.035
Normal hydration status: <1.007
Critical value(s) SG > 1.035 indicates contaminated specimen, high glucose
concentration, or recent intake of radiopaque dyes or IV
low-molecular-weight dextran.
Increased levels SG > 1.010 indicates relative dehydration.
Decreased levels SG ≤1.022 after 12-hour fast (no food or water) indicates im-
paired renal concentrating ability, as in renal dysfunction or
nephrogenic diabetes insipidus.
Interfering factors Contaminated specimen
Cross-references Diabetes Insipidus
Psychogenic Polydipsia
Urinalysis
American Association for Clinical Chemistry: Testing.com. Available at: https://www.testing.com. Ac-
cessed October 2021.
Fischbach FT, Fischbach MA: A Manual of Laboratory and Diagnostic Tests, 10th Edition. Philadelphia,
PA, Wolters Kluwer Health/Lippincott Williams and Wilkins, 2018
Simerville JA, Maxted WC, Pahira JJ: Urinalysis: a comprehensive review. Am Fam Physician 71:1153–
1162, 2005
https://t.me/med1917
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