4 Diagnostic Laboratory Studies in the ICU Patient: What, When, and How Often?

10.1055/b-0038-160234

4 Diagnostic Laboratory Studies in the ICU Patient: What, When, and How Often?

John Ogunlade, Dan E. Miulli, and Jon Taveau

Abstract

Diagnostic laboratory studies assist in excluding or confirming a diagnosis when combined with a thorough history and physical examination so that a treatment plan can ultimately be formulated and performed in a precise manner. Laboratory studies are not meant to be ordered indiscriminately but strictly and critically to unmask the underlying pathological process.

Case Presentation

An 18-year-old woman presents with acute onset of the worst headache of her life and decreased consciousness.

See end of chapter for Case Management.

4.1 Introduction

Diagnostic laboratory studies are tools used to enhance the overall clinical picture. They assist in excluding or confirming a diagnosis when combined with a thorough history and physical examination so that a treatment plan can ultimately be formulated and performed. Reassessing the patient and repeating diagnostic studies continue to confirm the diagnosis is accurate. This circular assessment sequence is the foundation of clinical medicine. It should be repeated as often as necessary.

In the intensive care unit (ICU) patient, every laboratory test order is critical to unmasking the underlying process, and proper use of every bit of information is imperative. Ordering multiple studies indiscriminately, the so-called shotgun approach, adds much confusion to the assessment as well as a terrible cost burden. By using a strict, sequenced, clinical approach to diagnosis, costs, mistakes, and misdiagnoses are lessened. ► Table 4.1 and ► Table 4.2 list common laboratory panels and normal laboratory values, respectively. This chapter serves to help streamline decision making in laboratory test selections and to better interpret the information provided by these tests.

**Table 4.1** Common laboratory panels ¹ , ² , ³ , ⁴ , ⁵ , ⁶ , ⁷
Adrenal function Cortisol Dexamethasone suppression test (DST) Cosyntropin Metyrapone test and corticotropin (ACTH)–releasing hormone (CRH) Stimulation Dehydroepiandrosterone sulfate (DHEA-S) 17-ketosteroids 17-hydroxycorticosteroids
Blood products Type and cross: blood group (ABO), type (Rh type), Rh cross-match Antibody Coombs’s antiglobulin (direct and indirect) HLA analysis Leukoagglutinin Platelet antibody
Cardiac markers CK CK-MB Troponin (I, t) Homocysteine (Hcy) Myoglobin
Coagulation PT INR Partial thromboplastin time, activated (aPTT) Bleeding time Platelet count
Comprehensive metabolic panel (CMP) Sodium Potassium Chloride Carbon dioxide BUN Creatinine Glucose Calcium Magnesium Phosphorus Total protein Albumin Alkaline phosphatase ALT AST Bilirubin, total
CSF analysis (routine) Color and clarity Gram stain C&S Cell count with differential (tubes 2 and 4) Protein Glucose
CSF analysis (selective for infection) LDH Lactate Protein Immunoglobulin IgG–albumin index IgG, IgA, and IgM against Borrelia, parasites, and viruses Gram and Ziehl–Neelsen stain, touch prep Bacterial, fungal, viral, and mycobacterial culture DNA amplification (PCR) for tuberculosis and viral pathogens Syphilis (VDRL and FTA) Lyme disease Candida albicans
CSF analysis (selective for cerebrovascular disease) Cystatin C Disseminated intravascular coagulopathy (DIC) PT INR Partial thromboplastin time, activated (aPTT) Bleeding time Platelet count D dimer Thrombin time (TT), thrombin clotting time Fibrin split products Protein C&S Antithrombin III Fibrinogen antithrombin (I) Coagulation factors Encephalopathy Folic acid Vitamin B₁₂ TSH, T4 ammonia Creatinine Glutamine (CSF)
Hemogram with differential (CBC) Hemoglobin Hematocrit Platelet count RBC count Red blood cell indices (MCV, MCH, MCHC) WBC count Absolute neutrophils, eosinophils, basophils, lymphocytes, and monocytes
Hypercoagulable states Protein C Protein S Antithrombin III Factor V Leiden (activated protein C) Homocysteine Anticardiolipin antibodies Lupus anticoagulant
Inflammation ESR CRP ANA Rheumatoid factor Uric acid
Liver function Total protein Albumin Alkaline phosphatase ALT AST Bilirubin, total Ammonia (NH₃) γ-glutamyltransferase (GGT) Prothrombin time (PT) Platelet count Serum protein electrophoresis
Renal function CBC CMP 24-hour urine creatinine 24-hour urine protein Creatinine clearance
Toxicology screen Acetaminophen Carbon monoxide Barbiturate Ethanol Ethylene glycol Cocaine Cyanide Benzodiazepines Tricyclic antidepressants Methanol Insulin
Abbreviations: ACTH, adrenocorticotropic hormone; ALT, alanine aminotransferase; ANA, antinuclear antibody; AST, aspartate aminotransferase; BUN, blood urea nitrogen; CBC, complete blood count; CK, creatine kinase; CK-MB, creatine kinase–MB mass; CMP, cytidine monophosphate; CRP, C-reactive protein; CSF, cerebrospinal fluid; DNA, deoxyribonucleic acid; ESR, erythrocyte sedimentation rate; FTA, fluorescent treponemal antibody; HLA, human leukocyte antigen; Ig, immunoglobulin; INR, international normalized ratio; LDH, lactate dehydrogenase; MCH, mean corpuscular hemoglobin; MCHC, mean corpuscular hemoglobin concentration; MCV, mean corpuscular volume; PCR, polymerase chain reaction; PT, prothrombin time; RBC, red blood cell; TSH, thyroid-stimulating hormone; VDRL, Venereal Disease Research Laboratory; WBC, white blood cell.

**Table 4.2** Normal laboratory values ¹ , ² , ³ , ⁴ , ⁵ , ⁶ , ⁷
Test	Specimen	Method	Normal range conventional units	SI units
Acetylcholine receptor antibody	Serum	Immunoassay	< 0.5 nmol/L	< 0.5 nmol/L
Acetylcholinesterase	RBC	Enzymatic colorimetry	11,000–15,000 U/L	11–15 kU/L
Adrenocorticotropic hormone (ACTH)	Plasma	Immunoassay	< 70 μg/mL	< 15 pmol/L
Alanine aminotransferase (ALT)	Serum	Enzymatic colorimetry	< 48 U/L	< 0.80 mkat/L
Albumin	Serum	Colorimetry	3.5–5.0 g/dL	35–50 g/L
Aldolase	Serum	Enzymatic colorimetry	< 8.1 U/L	< 135 nkat/L
Aldosterone	Serum	Immunoassay	Supine: < 16 ng/dL Upright: 4–31 ng/dL	Supine: < 444 pmol/L Upright: 111–860 pmol/L
Alkaline phosphatase Isoenzymes	Serum	Electrophoresis	Intestinal: < 18% of total activity Bone: 23–62% of total activity Liver: 38–72% of total activity	Intestinal: < 0.18 of total activity Bone: 0.23–0.62 of total activity Liver: 0.38–0.72 of total activity
Total	Serum	Enzymatic colorimetry	20–125 U/L	0.33–2.08 mkat/L
Ammonia	Plasma	Enzymatic colorimetry	0.17–0.80 mg/mL	10–47 μmol/L
Amylase	Serum	Enzymatic colorimetry	30–170 U/L	0.50–2.83 mkat/L
Androstenedione	Serum	Immunoassay	65–270 ng/dL Postmenopausal: < 180 ng/dL	2.3–9.4 nmol/L Postmenopausal: < 6.3 nmol/L
Angiotensin-converting enzyme (ACE)	Serum	Enzymatic colorimetry	8–52 U/L	133–867 nkat/L
Antidiuretic hormone (ADH)	Plasma	Extraction/immunoassay	< 2.2 μg/mL (serum Osm < 285 mOsm/kg)	2.2–8.5 μg/mL (serum Osm > 290 mOsm/kg)
			< 2.2ng/L (serum Osm < 285 mOsm/kg)	2.2–8.5 ng/L (serum Osm > 290 mOsm/kg)
Anti-DNA antibody (double-stranded)	Serum	Immunoassay	< 30 U/mL	< 30 kU/L
Antimicrosomal antibody (thyroid)	Serum	Immunoassay	< 0.3 U/mL	< 300 U/L
Antimitochondrial antibody	Serum	Immunofluorescence	Negative (< 1:20)
Antineutrophil cytoplasmic antibody (ANCA)	Serum	Immunofluorescence	Negative (< 1:20)
Antinuclear antibody (ANA)	Serum	Immunofluorescence	Negative (< 1:40)
Antithrombin III activity	Plasma	Nephelometry	85–130% of normal activity	0.85–1.3 of normal activity
Antithrombin III antigen	Plasma	Enzymatic colorimetry	25–33 mg/dL	250–330 mg/L
Antithyroglobulin antibody	Serum	Immunoassay	< 1 U/mL	< 1 kU/L
α1-antitrypsin	Serum	Nephelometry	80–200 mg/dL	0.8–2.0 g/L
Apolipoprotein A-I	Serum	Nephelometry	Male: 94–176 mg/dL	Male: 0.94–1.76 g/L
			Female: 101–198 mg/dL	Female 1.01–1.98 g/L
Apolipoprotein B	Serum	Nephelometry	Male: 52–109 mg/dL	Male: 0.52–1.09 g/L
			Female: 49–103 mg/dL	Female: 0.49–1.03 g/L
Apolipoprotein E	Serum	Nephelometry
Apolipoprotein E4	Serum	Nephelometry
Arsenic	Urine	ICP-MS	< 50 mg/d	< 0.65 mmol/day
Aspartate aminotransferase (AST)	Serum	Enzymatic colorimetry	< 42 U/L	< 0.7 mkat/L
Bilirubin
Direct	Serum	Colorimetry	< 0.4 mg/dL	< 7 mmol/L
Indirect	Serum	Colorimetry	< 1.3 mg/dL	< 22 mmol/L
Total	Serum	Colorimetry	< 1.3 mg/dL	< 22 mmol/L
Bleeding time, template	Not applicable	Template method	2.5–9.5 minutes
Cancer antigen (CA) 15.3	Serum	ABBOTT AXSYM	< 32 U/mL	< 32 kU/L
		CA15–3MEIA
CA 19.9	Serum	CIS ELSA-CA 19–9 IRMA	< 33 U/mL	< 33 kU/L
CA 27.29	Serum	BIOMIRA TRUQANT	< 38 U/mL	< 38kU/L
		BR RIA
CA 125	Serum	CENTOCOR-CA125IIRIA	< 35 U/mL	< 35 kU/L
Calcitonin	Serum	Immunoassay	Male: < 13.8 μg/mL	Male: < 13.8 ng/L
Calcitonin	Serum	Immunoassay	Female: < 6.4 μg/mL	Female: < 6.4 ng/L
Calcium	Serum	Colorimetry	8.5–10.3 mg/dL	2.12–2.57 mmol/L
	Urine	Colorimetry	Male: < 300 mg/d	Male: < 7.5 mmol/day
			Female: < 250 mg/d	Female: < 6.2 mmol/d
Carbon dioxide	Serum	Colorimetry	20–32 mmol/L	20–32 mmol/L
Carboxyhemoglobin	Blood	Spectrophotometry	< 2% of total Hb (nonsmoker)	< 0.02
Carcinoembryonic antigen (CEA)	Serum	CHIRON ACS: 180 ICMA	< 2.5 ng/mL (nonsmoker)	< 2.5 mg/L (nonsmoker)
Catecholamines Fractionated	Plasma	HPLC	Dopamine	Dopamine
			Supine: < 90 μg/mL	Supine: < 588 pmol/L
			Standing: < 90 μg/mL	Standing: < 588 pmol/L
			Epinephrine	Epinephrine
			Supine: < 50 μg/mL	Supine: < 273 pmol/L
			Standing: < 90 μg/mL	Standing: < 491 pmol/L
			Norepinephrine	Norepinephrine
			Supine: 110–410 μg/mL	Supine: 650–2423 pmol/L
			Standing: 125–700 μg/mL	Standing: 739–4137 pmol/L
Total	Plasma	HPLC	Supine: 120–450 μg/mL	Supine: 709–2660 pmol/L
			Standing: 150–750 μg/mL	Standing: 887–4433 pmol/L
Ceruloplasmin	Serum	Nephelometry	25–63 mg/dL	250–630 mg/L
Chloride	Serum	ISE	95–108 mmol/L	95–108 mmol/L
Cholesterol, total	Serum	Colorimetry	Desirable: < 200 mg/dL	Desirable: < 5.17 mmol/L
			Borderline-high:	Borderline-high:
			200–239 mg/dL	5.17–6.18 mmol/L
			High: > 240 mg/dL	High: > 6.21 mmol/L
Complement
C3	Serum	Nephelometry	75–161 mg/dL	0.75–1.61 g/L
C4	Serum	Nephelometry	16–47 mg/dL	0.16–0.47 g/L
Total (CH 50)	Serum	Liposome lysis	31–66 U/mL	31–66kU/L
Complete blood count (CBC)	Blood	Automated analyzer
Hemoglobin (Hb)			Male: 13.8–17.2 g/dL	Male: 138–172 g/L
			Female: 12.0–15.6 g/dL	Female: 120–156 g/L
Hematocrit (Hct)			Male: 41–50%	Male: 0.41–0.50
			Female: 35–46%	Female: 0.35–0.46
RBC count			Male: 4.4–5.8 × 10⁶/mL	Male: 4.4–5.8 × 10¹²/L
			Female: 3.9–5.2 × 10⁶/mL	Female: 3.9–5.2 × 10¹²/L
RBC indices			Mean corpuscular volume: 78–102 fL	Mean corpuscular volume: 78–102 fL
			Mean corpuscular Hb: 27–33 μg	Mean corpuscular Hb: 27–33 μg
			Mean corpuscular Hb concentration: 32–36 g/dL	Mean corpuscular Hb concentration: 320–360 g/L
			RBC distribution width: < 15%	RBC distribution width: < 0.15
WBC count			3.8–10.8 × 10³/μL	3.8–10.8 × 10⁹/L
WBC differential			Absolute neutrophils: 1,500–7,800 cells/mL	Absolute neutrophils: 1.5–7.8 × 10⁹/L
			Absolute eosinophils: 50–550 cells/mL	Absolute eosinophils: 0.05–0.55 × 10⁹/L
			Absolute basophils: 0–200 cells/mL	Absolute basophils: 0–0.2 × 10⁹/L
			Absolute lymphocytes: 850–4100 cells/mL	Absolute lymphocytes: 0.85–4.10 × 10⁹/L
			Absolute monocytes: 200–1100 cells/mL	Absolute monocytes: 0.2–1.10⁹/L
Platelet count			130–400 × 103/mL	130–400 × 10⁹/L
Cortisol, free	Urine	Immunoassay	20–90 mg/d	55–248 nmol/d
Cortisol	Serum	Immunoassay	4–22 mg/dL (morning specimen)	110–607 nmol/L (morning specimen)
			3–17 mg/dL (afternoon specimen)	83–469 nmol/L (afternoon specimen)
C-peptide	Serum	Immunoassay	0.8–4.0 ng/mL	0.26–1.32 nmol/L
C-reactive protein (CRP), creatine kinase (CK)	Serum	Nephelometry	< 0.8 mg/dL	< 8 mg/L
Isoenzymes	Serum	Electrophoresis	CK-MM: 97–100% of total	CK-MM: 0.97–1.00 of total
			CK-MB: < 3% of total	CK-MB: < 0.03 of total
			CK-BB: 0% of total	CK-BB: 0 of total
Total	Serum	Enzymatic colorimetry	Male: < 235 U/L	Male: < 3.92 mkat/L
			Female: < 190 U/L	Female: < 3.17 mkat/L
Creatinine	Serum	Enzymatic colorimetry	< 1.2 mg/dL	< 106 mmol/L
	Urine	Enzymatic colorimetry	Male: 0.8–2.4 g/d	Male: 7.1–21.2 mmol/day
			Female: 0.6–1.8 g/d	Female: 5.3–15.9 mmol/d
Creatinine clearance	Serum, urine	Calculation:	Male: 82–125 mL/min	Male: 1.37–2.08 mL/s
			Female: 75–115 mL/min	Female: 1.25–1.92 mL/s
Cyanide	Blood	Colorimetry	< 0.1 mg/L	< 3.8 mmol/L
D-dimer	Plasma	Slide latex agglutination	< 250 mg/L	< 250 mg/L
Dehydroepiandrosterone (DHEA), unconjugated	Serum	Immunoassay	130–1200 ng/dL	4.5–41.6 nmol/L
Dehydroepiandrosterone sulfate (DHEA-S)	Serum	Immunoassay	Male (age): 29 years 1.4–7.9 mg/mL	Male (age): 29 years 3.8–21.4 mmol/L
			30–39 years 1.0–7.0 mg/mL	30–39 years 2.7–19.0 mmol/L
			40–49 years 0.9–5.7 mg/mL	40–49 years 2.4–15.5 mmol/L
			50–59 years 0.6–4.1 mg/mL	50–59 years 1.6–11.1 mmol/L
			60–69 years 0.4–3.2 mg/mL	60–69 years 1.1–8.7 mmol/L
			70–79 years 0.3–2.6 mg/mL	70–79 years 0.8–7.1 mmol/L
			Female (age):	Female (age):
			29 years 0.7–4.5 mg/mL	29 years 1.9–12.2 mmol/L
			30–39 years 0.5–4.1 mg/mL	30–39 years 1.4–11.1 mmol/L
			40–49 years 0.4–3.5 mg/mL	40–49 years 1.1–9.5 mmol/L
			50–59 years 0.3–2.7 mg/mL	50–59 years 0.8–7.3 mmol/L
			60–69 years 0.2–1.8 mg/mL	60–69 years 0.5–4.9 mmol/L
			70–79 years 0.1–0.9 mg/mL	70–79 years 0.3–2.4 mmol/L
11-deoxycortisol	Serum	Immunoassay	< 0.8 μg/dL	< 23 nmol/L
Erythrocyte sedimentation rate (ESR)	Blood	Modified Westergren	Male: < 20 mm/h	Male: < 20 mm/h
			Female: < 30 mm/h	Female: < 30 mm/h
Erythropoietin	Serum	Immunoassay	< 25 U/L	< 25 U/L
Estradiol	Serum	Immunoassay	Male: < 50 μg/mL	Male: < 184 pmol/L
			Female:	Female:
			Follicular phase 10–200 μg/mL	Follicular phase 37–734 pmol/L
			Midcycle 100–400 μg/mL	Midcycle 367–1468 pmol/L
			Luteal phase 15–250 μg/mL	Luteal phase 55–954 pmol/L
			Postmenopausal < 50 μg/mL	Postmenopausal < 184 pmol/L
Estrone	Serum	Immunoassay	Male: 29–81 μg/mL	Male: 107–300 pmol/L
			Female:	Female:
			Follicular phase 37–152 μg/mL	Follicular phase 137–562 pmol/L
			Midcycle 72–200 μg/mL	Midcycle 266–740 pmol/L
			Luteal phase 49–114 μg/mL	Luteal phase 181–422 pmol/L
			Postmenopausal < 65 μg/mL (without HRT)	Postmenopausal < 240 pmol/L (without HRT)
Fatty acids, free	Plasma	Enzymatic colorimetry	0.19–0.90 mEq/L	0.19–0.90 mmol/L
Ferritin	Serum	Immunoassay	Male: 18–350 ng/mL	Male: 18–350 mg/L
			Female (age):	Female (age):
			15–49 years 12–156 ng/mL	15–49 years 12–156 mg/L
			> 49 years 18–204 ng/mL	> 49 years 18–204 mg/L
Fibrinogen	Plasma	Photo-optical clot detection	200–400 mg/dL	2–4 g/L
Folic acid	RBC	Immunoassay	> 95 ng/mL	> 215 nmol/L
	Serum	Immunoassay	> 1.9 ng/mL	> 4.3 nmol/L
Follicle-stimulating hormone (FSH)	Serum	Immunoassay	Male (age): 20–70 years: 0.9–15.0 U/L	Male (age): 20–70 years: 0.9–15.0 U/L
			> 70 years: 2.8–55.5 U/L	> 70 years: 2.8–55.5 U/L
			Female: follicular phase 1.1–9.6 U/L	Female: Follicular phase 1.1–9.6 U/L
			Midcycle 2.3–20.9 U/L	Midcycle 2.3–20.9 U/L
			Luteal phase 0.8–7.5 U/L	Luteal phase 0.8–7.5 U/L
			Pregnancy < 0.9 U/L	Pregnancy < 0.9 U/L
			Postmenopausal	Postmenopausal
			34.4–95.8 U/L	34.4–95.8 U/L
Free erythrocyte protoporphyrin (FEP)	Blood	Fluorometry	< 35 mg/dL RBGs	< 0.62 mmol/L RBGs
Fructosamine	Serum	Colorimetry	1.6–2.6 mmol/L	1.6–2.6 mmol/L
Gastrin	Serum	Immunoassay	< 200 μg/mL (nonfasting)	< 200 ng/L (nonfasting)
			< 100 μg/mL (fasting)	< 100 ng/L (fasting)
Glucagon	Plasma	Immunoassay	50–200 μg/mL	50–200 ng/L
Glucose
Fasting	Plasma	Enzymatic colorimetry	< 110 mg/dL	< 6.1 mmol/L
Random	Serum	Enzymatic colorimetry	70–125 mg/dL	3.9–6.9 mmol/L
Glucose-6-phosphate dehydrogenase (G6PD)	Blood	Enzymatic colorimetry	5–13 U/g Hb	5–13 U/g Hb
γ-glutamyl transferase (GGT)	Serum	Enzymatic colorimetry	Male: < 65 U/L	Male: < 1.08 mkat/L
			Female: < 45 U/L	Female: < 0.75 mkat/L
Growth hormone (GH)	Serum	Immunoassay	< 8 ng/mL	< 8 mg/L
Haptoglobin	Serum	Nephelometry	43–212 mg/dL	0.43–2.12 g/L
Hematocrit (Hct)	Blood	Automated analyzer	Male: 41–50%	Male: 0.41–0.50
			Female: 35–46%	Female: 0.35–0.46
Hemoglobin (Hb) A1c	Blood	Automated analyzer	Male: 13.8–17.2 g/dL	Male: 138–172 g/L
			Female: 12.0–15.6 g/dL	Female: 120–156 g/L
	Blood	HPLC	< 6.0% of total Hb	< 0.06 of total Hb
Electrophoresis	Blood	Electrophoresis	Hb A1: < 96.0%	Hb A1: < 0.96
			Hb A2: 1.5–3.5%	Hb A2: 0.015–0.035
			Hb C: 0%	Hb C: 0
			Hb F: < 2.0%	Hb F: < 0.02
			Hb S: 0%	Hb S: 0
High-density lipoprotein (HDL) cholesterol	Serum	Precipitation/colorimetry	> 35 mg/dL	> 0.9 mmol/L
			“Negative” risk factor: > 60 mg/dL	“Negative” risk factor: > 1.55 mmol/L
Homocysteine	Plasma	HPLC	6.1–17.0 mmol/L	6.1–17.0 mmol/L
Homovanillic acid	Urine	HPLC	< 10 mg/d	< 55 mmol/d
Human chorionic gonadotropin (hCG)
Qualitative	Urine	Immunoassay	Nonpregnant: negative
			Pregnant: positive
Quantitative (intact and free b)	Serum	Immunoassay	Male: < 2 U/L	Male: < 2 U/L
			Female:	Female:
			Premenopausal: < 5 U/L	Premenopausal: < 5 U/L
			Postmenopausal: < 10 U/L	Postmenopausal: < 10 U/L
			Pregnancy:	Pregnancy:
			0–2 wk < 500 U/L	0–2 wk < 500 U/L
			2–3 wk 100–5,000 U/L	2–3 wk 100–5000 U/L
			3–4 wk 500–10,000 U/L	3–4 wk 500–10,000 U/L
			1–2 months 1,000–200,000 U/L	1–2 months 1000–200,000 U/L
			2–3 months	2–3 months
			10,000–100,000 U/L	10,000–100,000 U/L
17-hydroxycorticosteroids	Urine	Enzymatic colorimetry	Male: 3–15 mg/d	Male: 8.3–41.4 mmol/d
			Female: 2–12 mg/d	Female: 5.5–33.1 mmol/d
5-hydroxyindoleacetic acid (5-HIAA)	Urine	HPLC	0.5–9.0 mg/d	3–47 mmol/d
Immunoglobulin
IgA	Serum	Nephelometry	81–463 mg/dL	0.81–4.63 g/L
IgD	Serum	Radial immunodiffusion	< 14 mg/dL	< 0.14 g/L
IgE	Serum	Immunoassay	< 180 U/mL	< 432 mg/L
IgG, subclasses	Serum	Nephelometry	Subclass IgG 1:450–900 mg/dL	Subclass IgG 1:4.5–9.0 g/L
			Subclass IgG 2: 180–530 mg/dL	Subclass IgG 2:1.8–5.3 g/L
			Subclass IgG 3:1380 mg/dL	Subclass IgG 3: 0.13–0.80 g/L
			Subclass IgG 4: 8–100 mg/dL	Subclass IgG 4: 0.08–1.00 g/L
IgC, total	Serum	Nephelometry	723–1685 mg/dL	7.23–16.85 g/L
IgM	Serum	Nephelometry	48–271 mg/dL	0.48–2.71 g/L
Insulin	Serum	Immunoassay	5–25 mU/mL	36–179 pmol/L
Iron	Serum	Colorimetry	25–170 mg/dL	4–30 mmol/L
Iron-binding capacity	Serum	Colorimetry	200–450 mg/dL	36–81 mmol/L
			% saturation: 12–57%	% saturation: 0.12–0.57
17-ketogenic steroids	Urine	Colorimetry	Male: 5–23 mg/d	Male: 17–80 mmol/d
17-ketosteroids, total			Female: 3–15 mg/d	Female: 10–52 mmol/d
	Urine	Colorimetry	Male: 9–22 mg/d	Male: 31–76 mmol/d
Lactate dehydrogenase (LD)			Female: 5–15 mg/d	Female: 17–52 mmol/d
Isoenzymes	Serum	Electrophoresis	LD1: 20–36% of total	LD1: 0.20–0.36 of total
			LD2: 32–50% of total	LD2: 0.32–0.50 of total
			LD3: 15–25% of total	LD3: 0.15–0.25 of total
			LD4: 2–10% of total	LD4: 0.02–0.10 of total
			LD5: 3–13% of total	LD5: 0.03–0.13 of total
Total	Serum	Enzymatic colorimetry	< 270 U/L	< 4.5 mkat/L
Lactic acid	Plasma (venous)	Enzymatic colorimetry	9–16 mg/dL	1.0–1.8 mmol/L
Lead	Blood	Atomic spectroscopy	< 25 mg/dL	< 1.21 mmol/L
Lipase	Serum	Enzymatic colorimetry	7–60 U/L	0.12–1.00 mkat/L
Low-density lipoprotein (LDL) cholesterol, direct	Serum	Immunoseparation	Desirable: < 130 mg/dL	Desirable: < 3.36 mmol/L
		Colorimetry	Borderline-high: 130–159 mg/dL	Borderline-high: 3.36–4.11 mmol/L
			High: > 160 mg/dL	High:> 4.14 mmol/L
Luteinizing hormone (LH)	Serum	Immunoassay	Male (age): 20–70 years	Male (age): 20–70
			1.3–12.9 U/L	years 1.3–12.9 U/L
			> 70 years 11.3–56.4 U/L	> 70 years 11.3–56.4 U/L
			Female:	Female:
			Follicular phase 0.8–25.8 U/L	Follicular phase 0.8–25.8 U/L
			Midcycle 25.0–57.3 U/L	Midcycle 25.0–57.3 U/L
			Luteal phase 0.8–27.1 U/L	Luteal phase 0.8–27.1 U/L
			Pregnancy < 1.4 U/L	Pregnancy < 1.4 U/L
Lymphocyte surface markers (T cell)			Postmenopausal 5.0–52.3 U/L	Postmenopausal 5.0–52.3 U/L
CD3	Blood	Flow cytometry	Absolute: 840–3060 cells/mL	Absolute: 0.84–3.06 × 109 cells/L
			Percentage: 57–85%	Percentage: 0.57–0.85 (57–85%)
CD4	Blood	Flow cytometry	Absolute: 490–1740 cells/mL	Absolute: 0.49–1.74 × 109 cells/L
			Percentage: 30–61%	Percentage: 0.30–0.61 (30–61%)
CD8	Blood	Flow cytometry	Absolute: 180–1170 cells/mL	Absolute: 0.18–1.17 × 109 cells/L
			Percentage: 12–42%	Percentage: 0.12–0.42 (12–42%)
Helper/suppressor (CD4/CD8) ratio	Blood	Flow cytometry	0.86–5.00	0.86–5.00
Magnesium	Serum	Colorimetry	0.6–1.0 mmol/L	0.6–1.0 mmol/L
Mercury metanephrines	Blood	Atomic spectroscopy	< 1 mg/dL	< 50 nmol/L
Fractionated	Urine	HPLC	Metanephrine: < 0.4 mg/d	Metanephrine: < 2.2 mmol/d
			Normetanephrine: < 0.9 mg/d	Normetanephrine: < 4.9 mmol/d
Total	Urine	HPLC	< 1.3 mg/d	< 7.1 mmol/d
Methemoglobin	Blood	Spectrophotometry	< 2% of total Hb	< 0. 02 of total Hb
β2-microglobulin	Serum	Immunoassay	< 3 mg/L	< 3 mg/L
Muramidase (lysozyme)	Serum	Turbidimetry	2.8–8. 0 mg/L	0.20–0.56 mmol/L
Myelin basic protein	CSF	Immunoassay	< 4 ng/mL	< 4 mg/L
Myoglobin	Serum	Immunoassay	< 55 ng/mL	< 55 mg/L
Nitrogen, total	Feces	Acid digestion/titrimetry	< 2 g/d	< 143 mmol/d
Osmolality	Serum	Freezing point depression	278–305 mOsm/kg	278–305 mmol/kg
	Urine	Freezing point depression	50–1200 mOsm/kg	50–1,200 mmol/kg
Oxalate	Urine	Colorimetry	< 40 mg/d	< 456 mmol/d
Parathyroid hormone (PTH), intact	Serum	Immunoassay	11–54 μg/mL	1.2–5.8 pmol/L
Partial thromboplastin time, activated (aPTT)	Plasma	Photo-optical clot detection	20–36 s	20–36 s
Phosphorus	Serum	Colorimetry	2.5–4.5 mg/dL	0.81–1.45 mmol/L
Platelet count	Blood	Automated analyzer	130–400 × 103/mL	130–400 × 109/L
Porphobilinogen	Urine	Column chromatography/spectrophotometry	< 2 mg/d	< 8.8 mmol/d
Porphyrins, fractionated (protoporphyrin)	Feces	HPLC	Dicarboxyporphyrin < 1,830 mg/d	Dicarboxyporphyrin < 3.26 mmol/d
			(protoporphyrin)
			Heptacarboxyporphyrin < 20 mg/d
			Octacarboxyporphyrin < 80 mg/d	Octacarboxyporphyrin < 96 nmol/d
			(uroporphyrin)	(uroporphyrin)
			Tetracarboxyporphyrin	Tetracarboxyporphyrin
			< 640 mg/d	< 977 nmol/d
			(coproporphyrin)	(coproporphyrin)
Potassium	Serum	ISE	3.5–5.3 mmol/L	3.5–5.3 mmol/L
Prealbumin	Serum	Nephelometry	18–45 mg/dL	180–450 mg/L
Progesterone	Serum	Immunoassay	Male: < 1.2 ng/mL	Male: < 3.8 nmol/L
			Female:	Female:
			Follicular phase < 1.4 ng/mL	Follicular phase < 4.5 nmol/L
			Luteal phase 2.5–28.0 ng/mL	Luteal phase 8.0–89.0 nmol/L
			Pregnancy	Pregnancy
			1st trimester	1st trimester
			9.0–47.0 ng/mL	28.6–149.5 nmol/L
			2nd trimester	2nd trimester
			17.0–146.0 ng/mL	54.1–464.3 nmol/L
			3rd trimester	3rd trimester
			55.0–255.0 ng/mL	174.9–810.9 nmol/L
			Postmenopausal < 0.7 ng/mL	Postmenopausal < 2.2 nmol/L
Prolactin	Serum	Immunoassay	Male: 2–18 ng/mL	Male:2–18 mg/mL
			Female:	Female:
			Nonpregnant 3–30 ng/mL	Nonpregnant 3–30 mg/L
			Pregnant 10–209 ng/mL	Pregnant 10–209 mg/L
			Postmenopausal 2–20 ng/mL	Postmenopausal 2–20 mg/L
Prostate-specific antigen (PSA)	Serum	Immunoassay	< 4 ng/mL (male)	< 4 mg/L (male)
Protein, total	Serum	Colorimetry	6.0–8.5 g/dL	60–85 g/L
	Urine	Colorimetry	< 150 mg/d	< 150 mg/d
Protein C activity	Plasma	Photo-optical clot detection	70–140% of normal	0.7–1.4 of normal
Protein C antigen	Plasma	Immunoassay	70–140% of normal	0.7–1.4 of normal
Protein electrophoresis	Serum	Electrophoresis	Albumin: 3.5–5.5 g/dL	Albumin: 35–55 g/L
			α₁-globulins: 0.1–0. 3 g/dL	α₁-globulins: 1–3 g/L
			α₂-globulins: 0.2–1.1 g/dL	α₂-globulins: 2–11 g/L
			β-globulins: 0.5–1.2 g/dL	β-globulins: 5–12 g/L
			γ-globulins: 0.5–1.5 g/dL	γ-globulins: 5–15 g/L
Protein S activity	Plasma	Photo-optical clot detection	Male: 70–150% of normal	Male: 0.7–1.5 of normal
			Female: 58–130% of normal	Female: 0.58–1.30 of normal
Protein S antigen	Plasma	Immunoassay	Male: 70–140% of normal	Male: 0.7–1.4 of normal
			Female: 70–140% of normal	Female: 0.7–1.4 of normal
Prothrombin time (PT)	Plasma	Photo-optical clot detection international normalized ratio (INR): 0.9–1.1 (patients not on anticoagulant therapy)	10.0–12.5 s	10. 0–12. 5 s
Protoporphyrin
Free erythrocyte	Blood	Fluorometry	< 35 mg/dL RBCs	< 0.62 mmol/L RBCs
Zinc	Blood	Fluorometry	< 70 mg/dL	< 700 mg/L
Pyruvate	Blood	Enzymatic colorimetry	0.3–0.9 mg/dL	34–102 mmol/L
Pyruvate kinase	Blood	Fluorometry	Enzyme activity detected
RBC count	Blood	Automated analyzer	Male: 4.4–5.8 × 10⁶/mL	Male: 4. 4–5. 8 × 10¹²/L
			Female: 3.9–5.2 × 10⁶/mL	Female: 3.9–5.2 × 10¹²/L
RBC indices	Blood	Automated analyzer	Mean corpuscular volume: 78–102 fL	Mean corpuscular volume: 78–102 fL
			Mean corpuscular Hb: 27–33 μg	Mean corpuscular Hb: 27–33 μg
			Mean corpuscular Hb	Mean corpuscular Hb
			concentration: 32–36 g/dL	concentration: 320–360 g/L
			RBC distribution width: < 15%	RBC distribution width: < 0.15
Renin activity	Plasma	Immunoassay	1.3–4.0 ng/mL/h (upright)	1.00–3. 07 nmol/L/h (upright)
			(Normal sodium intake: 100–200 mEq/d)	(Normal sodium intake: 100–200 mmol/d)
Reticulocyte count	Blood	Automated analyzer	0.5–2.3% of RBCs	0.005–0.023 of RBCs
Rheumatoid factor	Serum	Nephelometry	< 40 U/mL	< 40 kU/L
Schilling test	Urine	Radio-isotopic measurement	> 7% of administered dose in 24-hour urine	> 0.07 of administered dose in 24-hour urine
Scleroderma antibody (Scl-70)	-70) Serum	Immunoassay	Negative
Serotonin	Blood	HPLC	46–319 ng/mL	0.26–1.81 mmol/L
Sodium	Serum	ISE	135–146 mmol/L	135–146 mmol/L
Somatomedin-C	Serum	Immunoassay	Male: 90–318 ng/mL	Male: 90–318 mg/L
			Female: 116–270 ng/mL	Female: 116–270 mg/L
T3 (triiodothyronine) Free	Serum	Immunoassay	230–420 μg/dL	3.5–6.5 pmol/L
Reverse	Serum	Immunoassay	2.6–18.9 ng/dL	0.04–0. 29 nmol/L
Total T4 (thyroxine)	Serum	Immunoassay	60–181 ng/dL	0.9–2. 8 nmol/L
Free	Serum	Immunoassay	0.8–1.8 ng/dL	10–23 pmol/L
Total	Serum	Immunoassay	4.5–12.5 mg/dL	58–161 nmol/L
Testosterone, total	Serum	Immunoassay	Male: 194–833 ng/dL	Male: 6.7–28.9 nmol/L
			Female: 62 ng/dL	Female: < 2.1 nmol/L
Thrombin time	Plasma	Photo-optical clot detection	10.0–13.5 s	10.0–13.5 s
Thyroglobulin	Serum	Immunoassay	< 60 ng/mL	< 60 mg/L
Thyroid-stimulating hormone (TSH), ultrasensitive (third generation)	Serum	Immunoassay	0.50–4.70 mU/mL	0.50–4.70 mU/L
Thyroxine-binding globulin (TBG)	Serum	Immunoassay	16–34 mg/L	16–34 mg/L
Transferrin	Serum	Nephelometry	188–341 mg/dL	1.88–3.41 g/L
Triglycerides	Serum	Enzymatic colorimetry	< 200 mg/dL	< 2.26 mmol/L
Urea nitrogen, blood (BUN)	Serum	Colorimetry	7–30 mg/dL	2.5–10.7 mmol urea/L
Uric acid	Serum	Enzymatic colorimetry	Male: 4.0–8.5 mg/dL	Male: 238–506 mmol/L
			Female: 2.5–7.5 mg/dL	Female: 149–446 mmol/L
	Urine	Enzymatic colorimetry	200–750 mg/d	1.2–4.5 mmol/d
Urinalysis, complete	Urine	Reagent-impregnated strips	Appearance: clear, yellow
		Microscopy	Specific gravity: 1.001–1.035
			pH: 4.6–8.0
			Protein: negative
			Glucose: negative
			Reducing substances: negative
			Ketones: negative
			Bilirubin: negative
			Occult blood: negative
			WBC esterase: negative
			Nitrite: negative
			WBC: < 5/high-power field
			RBC: < 3/high-power field
			Renal epithelial cells: < 3/high-power field
			Squamous epithelial cells: none or few/high-power field
			Casts: none
			Bacteria: none
			Yeast: none
Vanillylmandelic acid (VMA)	Urine	HPLC	< 10 mg/d	< 50 mmol/d
Viscosity	Serum	Viscometer	1.5–1.9 viscosity units (relative to water)
Vitamin A	Serum	HPLC	30–95 mg/dL	1.05–3.32 mmol/L
Vitamin B₆	Plasma	HPLC	5–24 ng/mL	30–144 nmol/L
Vitamin B₁₂	Serum	Immunoassay	200–800 μg/mL	> 150–590 pmol/L
Vitamin C	Plasma	Colorimetry	0.2–2.0 mg/dL	11–114 mmol/L
1,25-dihydroxy-vitamin D	Serum	Chromatography	24–65 μg/mL	58–156 pmol/L
25-hydroxy-vitamin D	Serum	Acetonitrile extraction/immunoassay	10–55 ng/mL	25–137 nmol/L
Vitamin E	Serum	Fluorometry	5–20 mg/mL	12–46 mmol/L
WBC count	Blood	Automated analyzer	3.8–10.8 × 10³/mL	3.8–10.8 × 10⁹/L
WBC differential	Blood	Automated analyzer	Absolute neutrophils: 1,500–7,800 cells/mL	Absolute neutrophils: 1.5–7.8 × 10⁹/L
			Absolute eosinophils: 50–550 cells/mL	Absolute eosinophils: 0.05–0.55 × 10⁹/L
			Absolute basophils: 0–200 cells/mL	Absolute basophils: 0–0.2 × 10⁹/L
			Absolute lymphocytes: 850–4100 cells/mL	Absolute lymphocytes: 0.85–4.10 × 10⁹/L
			Absolute monocytes: 200–1100 cells/mL	Absolute monocytes: 0.2–1.10⁹/L
Zinc	Plasma	Atomic spectroscopy	60–130 mg/dL	9.2–19.9 mmol/L
Abbreviations: CSF, cerebrospinal fluid; DNA, deoxyribonucleic acid; HPLC, high-performance liquid chromatography; HRT, hormone replacement therapy; ICMA, immunochemiluminometric assay; ICP-MS, inductively coupled mass spectroscopy; IRMA, immunoradiometric assay; ISE, ion-selective electrode; MEIA, microparticle enzyme immunoassay; RBC, red blood (cell) count; RIA, radioimmunoassay; SI, International System of Units; WBC, white blood (cell) count.