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Lab Manual for UCSF Clinical Laboratories

Lab Manual for SFGH

Internal Resources

Toxicology Procedures



I. General Instructions


A. Requisitions and Specimen Delivery:

Use the “Main Laboratory Requisition for Urine/Fluids” or Order Entry in the SMS Hospital system when requesting urine toxicology tests. Use the “Main Laboratory Requisition for Blood” or Order Entry when requesting Therapeutic Drug or Ethanol concentrations in serum.

Deliver Toxicology specimens to the Clinical Laboratory (2M2).


B. Requesting Toxicology Tests

Some toxicology tests are performed only after consultation with a Clinical Chemistry/Toxicology Fellow or Lab Medicine Resident (See the Alphabetical List of Tests for further information). A Clinical Chemistry/Toxicology Fellow is available Monday - Friday, 9 am - 5 pm; call the Clinical Laboratory Information Section, 206-8590 to contact the fellow on call for consultation regarding toxicology problems: At all other times, page the Lab Medicine Resident on-call, pager (415) 443-6969 or call the Clinical Laboratory Information Section, 206-8590, to contact the Resident on-call.


Serum Testing

The Clinical Laboratory provides quantitative testing of serum for acetaminophen, carbamazepine, digoxin, ethylene glycol, gentamicin, lithium, methanol, phenobarbital, phenytoin, salicylates, tobramycin, valproic acid and vancomycin. STAT service is available 24 hours/day, 7 days/week except for methanol and ethylene glycol (8 am to 11 pm Mon to Fri and 8 am to 4 pm on Sat/Sun). See the appropriate listings in the Alphabetical List of Tests and the Table of Therapeutic/Toxic Ranges below for further details. The SFGH Clinical Laboratory does NOT screen serum for unknown drugs.


Urine Testing

To screen for unknown drugs, the only specimen type tested at the SFGH Clinical Laboratory is urine. Most drugs are present in higher concentrations and for a longer time in urine than in serum. With few exceptions, urine testing is more sensitive than serum for this purpose. If a patient has no urine output and serum testing is the only option, the specimen must be sent to a referral laboratory with a minimum turn-around time of 3-5 days and limited drug menu/sensitivity. Serum toxicology screening must be approved by the Clinical Chemistry Laboratory Medicine Resident (206-5527, pager (415) 443-2311).


Qualitative drug testing of urine is available at SFGH with several levels of service. See information below and appropriate listings in the Alphabetical List of Tests for more details ( Drug Screen, Comprehensive, and Drugs of Abuse Screen).


1) Single Tests - Automated immunoassay tests for Drugs of Abuse in urine can be ordered individually. STAT service with same day turn-around time for screening results is available 24 hours/day, 7 days/week. Confirmatory testing is performed routinely Mon-Fri with 1 to 4 day turn-around times. Confirmatory testing is no longer performed by default - confirmatory tests, if clinically indicated, must be requested in addition to screening tests. Available tests are:


Automated Immunoassay Screen

Confirmatory Assay

Amphetamines/Ecstasy class

LC/MS/MS (liquid chromatography-tandem mass spectrometry)

Barbiturates class

GC/MS (gas chromatography-mass spectrometry)

Benzodiazepines class

Not confirmed

Cocaine metabolite

Not confirmed

Ethanol (enzymatic assay)

Not confirmed

Methadone metabolite (EDDP)

GC/MS

Opiates class

LC/MS/MS

Oxycodone

LC/MS/MS

Phencyclidine (PCP)

GC/MS

2) Immunoassay Panels - Two panels of Drugs of Abuse automated immunoassay tests are available. One panel is used for the Emergency Department and a different panel is used for all other locations (see list of tests for each panel below). STAT service with same day turn-around time for screening results is available 24 hours/day, 7 days/week. Confirmatory testing is performed routinely Mon - Fri with 1 to 4 day turn around times.


Please note that toxicology testing at SFGH is performed for clinical use only. In particular - unconfirmed or presumptive results cannot be equated with drug use for a forensic or judicial (parole, custody, employment, denial of insurance) purpose.


Drugs of Abuse Screen – ED

Drugs of Abuse Screen - Other Locations

Amphetamines

Amphetamines

Benzodiazepines

Barbiturates

Cocaine metabolite

Benzodiazepines

Opiates

Methadone metabolite

Oxycodone

Opiates Oxycodone


3) Broad Spectrum Testing - Two options for broad spectrum (comprehensive) toxicology testing are available. The Drug Screen Urine, Comprehensive and Drug Screen Urine, Comprehensive with Consult test for a wide menu of illegal, over-the-counter, and prescription drugs. For most inpatient locations - laboratory consult is a prerequisite to obtain Broad Spectrum testing. Comprehensive screening with consult requires submission of a drug history and reason for testing (written on the requisition, or consult the Clinical Chemistry/Toxicology Fellow by calling the Clinical Laboratory Information Section, 206-8590 to contact the fellow on call Monday – Friday, 9 am – 5 pm). At all other times, page the Lab Medicine Resident on-call, pager (415) 443-6969). See “Use of Toxicology Tests, Section C.,” below, for more information on the benefits of using the “with consult” option.


These testing protocols include the immunoassays listed in (1) above and in addition use chromatography and mass spectrometry techniques to identify several hundred other drugs. Routine service is available Mon-Fri, 8 am to 5 pm with turn-around time of 1 to 4 days. STAT “comprehensive screens” are rarely indicated and are not provided by Toxicology. Call the California Poison Control Center for consultation on emergency diagnosis and management, product formulations and toxic potential (1-800-876-4766). Consult the Clinical Chemistry/ Toxicology Fellow (call the Clinical Laboratory Information Section, 206-8590 for the fellow on call Monday – Friday, 9 am – 5 pm) to discuss choice of tests, drugs that can or cannot be detected at SFGH, detection windows, and interpretation of test results.


Contact Information:

  1. California Poison Control Center, 24-hour hotline 1-800-876-4766, for emergency diagnosis and management consultation, product formulations and toxic potential.

  2. Clinical Laboratory, ext. 8590 for method information and results.

  3. Clinical Pharmacology, 502-6044, 8:30 am-4:30 pm; after hours call Poison Control Center for on-call referral, drug interactions, therapeutic drug monitoring consultation.


II. Use of Toxicology Tests


A. Toxicology screening following suspected overdose is usually used to confirm a clinical diagnosis of drug-induced disease or to differentiate drug-induced disease from other diagnoses (e.g. trauma, metabolic, or infectious encephalopathy) or contributing diagnoses (e.g. ethanol + head trauma, amphetamines + underlying psychosis). Rarely, drug screening or quantification may be predictive and may be used to direct future management (e.g. ethylene glycol, salicylate, and/or acetaminophen overdose).


In many circumstances management will not depend on laboratory testing, due to the advantage of early benign intervention, the use of clinical assessments that are more rapid than the laboratory test, or both. Such interventions include naloxone for opiates, vitamin B6 for isoniazid, vitamin K for warfarin, oxygen for carbon monoxide, methylene blue for methemoglobinemia, thiosulfate for cyanide.


B. Certain higher risk or more expensive interventions may be predicated on drug/toxin quantification, including: fomepizole for methanol or ethylene glycol, hemodialysis for ethylene glycol, lithium, methanol, salicylates or theophylline, deferoxamine for iron.


C. Optimal use of toxicology tests requires knowledge of drug metabolism and the details of test performance. The Toxicology Laboratory encourages providers to consult the Clinical Chemistry/ Toxicology Fellow (call the Clinical Laboratory Information Section, 206-8590, for the fellow on call Monday – Friday, 9 am – 5 pm) to discuss choice of tests and interpretation of results for acute or chronic overdose, substance abuse detection and treatment, or compliance testing.


If drugs or toxins other than the common drugs of abuse are suspected, consider using the Drug Screen Urine, Comprehensive with Consult . After receiving a complete drug history and reason for testing (written on the requisition form or consult the Clinical Chemistry/ Toxicology Fellow [call the Clinical Laboratory Information Section, 206-8590 for the fellow on call Monday – Friday, 9 am – 5 pm]), screening will be directed based on the information submitted. Results will include an interpretation, focused on the capability, or lack of capability, of the SFGH testing process to rule out or confirm toxins of interest. The value of broad spectrum screening is significantly enhanced by choosing the consult option. Thousands of drugs and toxins may affect your patient, and not all of them can be detected at once. Testing without consult can identify the most common drugs seen in overdose. Testing with consult refines the testing process to:


  • identify more drugs of clinical interest

  • find drugs present at therapeutic and sub-therapeutic concentrations

  • detect rarely seen or difficult to identify drugs

  • clarify when drugs of interest cannot be ruled out because of technology limitations



THERAPEUTIC DRUG MONITORING (TDM) IN SERUM


Name

(Brand Names)

Therapeutic Range

Toxic Range

Additional Info

Acetaminophen

(Tylenol)

10-30 mg/L

> 50 mg/L

Half life: 2-4 hrs.

Elevated levels may cause hepatotoxicity.

Carbamazepine

(Tegretol)

4-10 mg/L

> 12 mg/L

Half life: 5-27 hrs.

Possible side effect - aplastic anemia.

Digoxin

(Lanoxin)

0.5-2.0 mcg/L

> 2.0 mcg/L

Half life: 1.6-5 days

May be false positive in uremic patient sample.

Gentamicin

(Garamycin, Genicin,

Gentisome)

5-10 mg/L – Peak

1-2 mg/L – Trough

Peak > 12 mg/L


Half life: 2-4 hrs.

Lithium

0.5 -1.5 mmol/L

> 2 mmol/L

Half life: 18-36 hrs.

Elevated levels may cause neurological problems.

Phenobarbital

(Barbital, Luminal, Solfoton)

15-40 mg/L

> 50 mg/L

Adult Half life: 50-120 hrs.

Child Half life: 40-70 hrs.

Phenytoin

(Dilantin)

10-20 mg/L

> 35 mg/L

Adult Half life: 18-30 hrs. (dose dependent)

Salicylate

(Aspirin, Acetyl Salicylic Acid, Excedrine)

Up to 25 mg/dL

> 35 mg/dL

lethal > 60 mg/dL

Half life: 2-4.5 hrs.

Child Half life: 2-3 hrs.

Tobramycin

(Nebcin)

5-10 mg/L – Peak

0.5-2 mg/L - Trough

> 12 mg/L - Peak


Half life: 2-3 hrs.

Elevated levels may cause nephrotoxicity.

Valproic Acid

(VPA, Depakene, Depakote, Epilim)

50-100 mg/L

> 350 mg/L

Half life: 8-15 hrs. Elevated levels may cause hyperammonia, acidosis and coma.

Vancomycin

(Vancocin)

20-40 mg/L – Peak

5-15 mg/L – Trough

> 80 mg/L - Peak


Half life: 4.7-7.8 hrs.

Elevated levels may cause ototoxicity, nephrotoxicity, and hypersensitivity reactions.



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