DRUG SCREEN URINE, COMPREHENSIVE and DRUG SCREEN URINE, COMPREHENSIVE with CONSULT (In LCR, see Urine Drug Confirmation - Add. Drugs Detd. for Broad Spectrum Testing results)
|Test code||CDS and CDSC (with consult)|
|In House Availability||Monday - Friday, 8:00 am - 5:00 pm
See also tests for single drugs/drug classes (e.g. opiates) OR Drugs of Abuse Screen, Urine as alternatives to monitor or rule out commonly encountered drugs of abuse with rapid turn-around time.
|Principle|| SCOPE of DRUG SCREEN URINE, COMPREHENSIVE TESTING:
The automated immunoassays listed for Drugs of Abuse Urine, Screen are part of the Comprehensive Drug Panel. In addition, the table below lists specific drugs, by drug class, that can be identified, and important drugs/drugs classes that CANNOT BE RULED OUT with this protocol for comprehensive drug testing.
The value of broad spectrum screening is significantly enhanced by choosing the Drug Screen Urine, Comprehensive with Consult. After receiving a complete drug history and reason for testing (written on the requisition or consult the Clinical Chemistry/Toxicology Fellow by calling the Clinical Laboratory Information Section, x68590 to contact the fellow on call Monday – Friday 9 am – 5 pm - screening will be directed based on the information submitted and 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. 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 technological limitations
|Method||High performance liquid chromatography, gas chromatography, mass spectrometry, immunoassays, and enzymatic assays. Qualitative (present or not present), rather than quantitative, results are reported for urine specimens.|
|Interpretation||Depending on the drug/drug class and testing method, some compounds are reported as "presumptive positive" if they have been detected with only a single method. Drugs that have been detected with two different methods are reported as "confirmed positive". Detection with two methods provides the best specificity, but is not always possible because of the individual chemical properties of drugs and technical characteristics of each analytical method.
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.
A number of other drugs can be detected and reported. The best yield from comprehensive drug testing is obtained when suspected agents are listed on the requisition form OR through consultation with the Clinical Chemistry/Toxicology Fellow (call the Clinical Laboratory Information Section, x68590 to contact the fellow on call Monday – Friday 9 am – 5 pm). Tox screens have a greater rule-in value than rule-out since not all toxins can be detected.
For several reasons, broad spectrum toxicologic screening has limited clinical utility unless it is used very selectively:
1. At best, broad spectrum toxicologic testing can detect and confirm a limited menu of drugs (perhaps 1,000 - 1,200) of more than 10,000 known toxins. The testing is designed to detect drugs most commonly seen in overdose (i.e., analgesics, antidepressants, street drugs, etc.), but there are important exceptions. For example, oral hypoglycemics and rodenticides are among the many other chemicals that are not detected.
2. Because of the desire to detect a wide selection of substances, sensitivity may be sacrificed for some drugs (analytical false negatives). Therefore, a drug may be on the list of substances that can be detected and may be affecting the patient – but if the amount of drug in the urine is below the limit of detection for that drug, it would not be reported as positive.
3. For these reasons, a comprehensive drug screen with no drugs detected does not rule out poisoning. Negative predictive values of 60-70 % have been published. However, predictive values are highly dependent on the prior probability of the test condition (prevalence of drug ingestion) and may therefore be lower for certain drugs or patient populations. Alternatively, a drug may be reported as positive from a comprehensive drug screen, but not be causing clinical symptoms (clinical false positive). Positive predictive values in the range of 90 % have been found in some studies.
4. As a result of these technical factors, as well as turn-around time and availability limitations, broad spectrum toxicologic testing is thought to affect management in only 5-15 % of cases. Situations where such testing may be useful include: Patients who are obtunded, have altered mental status, for whom the etiology of the original clinical problem is unknown, or to verify ingestion of suspected substances for psychosocial reasons. The best way to improve the yield of toxicologic testing is to communicate with the laboratory regarding suspected drugs, or if you suspect a "false" negative.
|Min. Volume||30 mL|
|Normal range||No drugs detected. See Interpretation for Drugs of Abuse Urine, Screen, for Detection Periods for specific drugs.|
|Synonyms||Comprehensive Drug Screen;Toxicology;|
|Stability||24 hours at 25°C, two weeks at 2-8°C, one month at -20°C.|
|Turn around times||Screening results are reported within 1 to 8 hours. (STAT/ Routine) as "Negative" or "Positive, Unconfirmed". Broad spectrum screening and confirmation: 48-72 hours for specimens received Mon – Fri; up to 4 days for specimens received after Fri 10:00 am.|
|Additional information||For evaluation of comatose, seizing, bizarre-acting patients where the differential diagnosis includes drug toxicity. Appropriate for detection of synthetic opiates (e.g. meperidine [Demerol], propoxyphene [Darvon], Tramadol [Ultram]), abused prescription and over-the-counter drugs (e.g. dextromethorphan, carisoprodol [Soma]), tricyclic and SSRI antidepressants, phenothiazine and atypical antipsychotic agents. Not indicated for rapid assessment, or to rule out of drugs of abuse, or for forensic testing.
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.
|References||1. Microgenics Amphetamine/Ecstasy 10006576-0 2003-1; Barbiturate 98-692-5 2002-09; Benzodiazepines 10006458-0 2002-11; Cocaine metabolite 10006475-0 2002-09; Methadone 10006542-0 2003-01; Methadone metabolite 10002371-2 2001-02; Opiates 98-695-3 2001-07; Phencyclidine 0141-1 2003-4; Ethanol 0318-1 August 2000. Microgenics Corporation, Fremont, CA.
2. Annual Report of the American Association of Poison Control Centers Toxic Exposure Surveillance System. Am J Emerg Med 2002; Sep 20(5):391-452.
3. Impact of toxicology screen in the diagnosis of a suspected overdose: Salicylates, tricyclic antidepressants, and benzodiazepines. Vet Hum Toxicol 1991; 33(1):40-43.
4. Utility and reliability of emergency toxicology testing. Emergency Medicine Clinics of North America. 1990; 8(3):693-722.
5. National Academy of Clinical Chemistry Laboratory Medicine Practice Guidelines: Recommendations for the Use of Laboratory Tests to Support Poisoned Patients Who Present to the Emergency Department. Clinical Chemistry, 2003; 49:357-379.
|Last Updated||6/17/2011 1:15:01 PM|