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Chemistry I. General Information A. Technologists are on-call only in Toxicology and Special Chem. The Core Chemistry (Fast Flow) lab is staffed by technologists 24 hrs/7days a week. Follow the steps below to call in a tech after hours for a test that you have determined needs to be performed. If a test is not described in this chemistry on-call manual, the test is not available in-house in Toxicology and Spec. Chem. Refer to the current edition of the Test Directory and Specimen Collection Handbook. Call Client Services ext 2-0707 or Laboratory Support Services (LSS) ext 2-4231 for send-out testing information. 1. LSS informs the requesting physician that the requested drug or test concentration requires approval of the resident. The physician is instructed to call the resident on call. 2. The resident returns the physician’s page and obtains clinical information and the reason for the test request. 3. The resident then has the authority to call in the technologist to perform the test. Call in a technologist only when it is clear to you that the request is justified by clinical and laboratory data. The technologist may ask the CP resident whether the questions below in B. 4-7 have been discussed with the ordering physician. 4. The technologist is then called in to do the test. B. Before calling a technologist you MUST get the following information:
C. Toxicology Laboratory Hours of Operation 1. The toxicology technologists work 8 a.m. to 5 p.m. Mon.-Fri. When they are called back to perform “Stat” tests, it becomes costly due to the overtime pay. Please use careful judgment in making your decision to call in a technologist. Calling in a technologist after hours should be limited to true medical emergencies only. 2. The on-call toxicology and electrophoresis tech has beeper #7420. D. Critical Value Notification The technologist performing the requested test is generally the person responsible for contacting the ordering physician of a critical value. Occasionally the tech may need to discuss the results with the resident who approved the test. If the ordering physician is not known, follow the procedure for critical value notification. Refer to the flow chart “Critical Value Notification,” in Appendix 1. E. Legal and Forensic Samples Legal samples are not accepted by the Clinical Laboratories. Refer to the Division of Laboratory Services policy “Chain of Custody and Forensic Specimens,” Appendix 1. II. Drug Testing That Never Need Approval A. SERUM: Quantitative assays for the drugs listed in Table 1 are performed by a rapid automated, analyzer 24 hours/day, 7 days/week in the Fast Flow Chemistry Laboratory.
B. URINE: Qualitative screening for Drugs of Abuse (DOA) listed in Table 2 is performed with the EMIT immunoassay on the Beckman-Coulter LX20 rapid automated chemistry analyzer 24 hours/day; 7 days/week in the Fast Flow Chemistry Lab. C. SERUM drug screen is not done in-house. Referred testing is available. D. The urine drug screen includes the following drug classes:
• Urine is the only specimen used in-house for drug screen testing. • The drug concentration in urine is NEVER reported by the screening method. • The urine drug screen is a qualitative test and the results are either negative or positive. Urine screens are reported positive if the drug is detected at a level above that of a positive calibrator as shown in Table 2. Confirmation testing of positive urine drug screens is not done in-house. Referral testing is available. • The cut-off levels for immunoassays have been established by various agencies in the US government (HHS, DOT, and DOD). See Reference 2. pg 941. • Flunitrazepam (Rohypnol), sometimes referred to as the “date-rape drug” is a benzodiazepine derivative. If present in high concentrations, it will give a positive reaction in the DOA benzodiazepine screen. • LSD testing is not available in-house. III. Drugs That Need Approval to Call a Toxicology Technologist The drug assays listed in Tables 3A and 3B are performed in the Special Chemistry laboratory as routine and “Stat” tests if received between 8 a.m. and 4:30 p.m, Mon.-Fri. During these hours, resident approval is not required. If a “Stat” is ordered before or after these hours Mon.-Fri. or after 11:30 a.m. Sat. and Sun., the testing must be approved by the resident before a technologist is called in. A. The therapeutic drug assays listed in Tables 3A and 3B are performed by procedures that require manual preparation of samples, controls, and calibrators. Allow at least one hour to complete, if a tech is in the lab and the instrument is turned on. Allow 2-3 hours to complete if the tech is called in and has to start up the instrument.
B. The drugs listed in Table 3. B are performed by high pressure liquid chromatography (HPLC) or spectrophotometric methods requiring labor-intensive, manual sample preparation. Allow approximately 2 hours to complete.
IV. Lead Levels Blood lead is done in the Tox. lab as a routine test once a week. Generally the assay is performed only on Friday. If a request for “Stat” blood lead is received at any time other than Friday, consultation between the ordering physician and the resident and/or one of the attending faculty is required for the test to be approved for “Stat” testing. The analysis is done on the graphite furnace atomic absorption spectrometer and requires approximately 1 hour to complete. V. Volatiles and Glycols. Refer Also to Appendix 2 <CLICK TO GOTO>. Volatiles: methanol (MeOH), isopropanol, ethanol (EtOH), and acetone. Glycols: ethylene glycol and propylene glycol. The assays for these substances are performed in the Toxicology lab as routine and “Stat” tests Mon.-Fri. if the sample is received between 8:00 a.m. and 4:30 p.m. If ordered before or after these hours Mon.-Fri. or on the weekend, approval is required to call in the toxicology technologist. Each of these tests requires approximately 1.5 hours to complete. If the volatiles and glycols are ordered at the same time, the turnaround time will be at least 3 hours. Allow more time if the tech is called-in. A. Volatiles in whole blood: MeOH Identification and quantitation are performed by gas chromatography analysis of the vapor phase (“headspace GC”) of the sample. Occasionally, urine is used as the sample. The four volatiles can be measured simultaneously. Serum EtOH quantitation is available 24 hours/7 days a week in the Core Chemistry (Fast Flow) Lab. See Section II. B. Serum ethylene glycol and propylene glycol. Identification and quantitation are performed by gas chromatography analysis. C. Before approving the test, the resident should first review Appendix 2 and ask the following questions: 1. Ask for the clinical diagnosis and for other information such as: • Is this an emergency: is the pt. stuporous, obtunded, or comatose? • Is there a strong suspicion to believe ingestion has occurred? Clinical signs for suspected MeOH, ethylene and propylene glycol: • MeOH: vomiting, coma, seizures, visual disturbances, motor restlessness. • Ethylene or propylene glycol: altered mental “Stat”us, acidosis, seizures, coma, appears drunk but no ethanol smell on breath. With ethylene glycol poisoning, decreased serum calcium, and, in the late phase of metabolism, calcium oxalate crystals in the urine are significant findings. Antifreeze is the most common source of ethylene glycol. • Propylene glycol is toxic (causes acidosis) even at low concentrations in children and in adults with renal impairment. Propylene glycol is widely found in the ”inert” matrix of OTC medications (e.g.,Tylenol), prescription drugs, cosmetics, toothpaste, and in household cleaning products, antifreeze, and other industrial solutions. 2. Ask whether the following tests have been ordered. All are available 24/7:
Urine drug screen for DOA 3. Always have serum bicarbonate, blood pH, serum/urine ketones and serum EtOH done before approving the tests for volatiles or glycols. Insist that the anion gap and a measured and calculated osmolality be orderd. 4. Refer to Appendix 2 for calculations and the decision algorithm that are used with the above lab tests for the laboratory evaluation of exogenous toxicities. VI. Hemoglobins S, C, F, A, and A2; Beta-2 transferrin A. These four hemoglobins are identified and quantitated by high performance liquid chromatography in the Special Chemistry lab. 1. If the sample is received as a routine or a ““Stat”” during regular hours 8:00 a.m.- 4:00 p.m. Mon.-Fri., the testing will be done the same day. The resident’s approval is not required 2. If ordered ““Stat”” before or after regular hours Mon.-Fri. or on the weekend, the resident’s approval is required to call in the electrophoresis tech. The on-call tech has beeper #7420. 3. Approval is always given for patients in sickle cell crisis, acute chest syndrome, hemolytic crisis, aplastic crisis, and other similar emergencies. B. Beta-2 transferrin for suspected CSF leakage 1. If ordered ““Stat”” before or after regular hours Mon.-Fri. or on the weekend, the resident’s approval is required to call in the electrophoresis tech. The on-call tech has beeper #7420. 2. This is an electrophoresis and immunofixation procedure that takes at least 3 hours to complete. VII. HIV-Rapid ”Stat” Test, as information. Resident approval is not needed. The OraQuick Rapid HIV-1 Antibody Test is available 24 hrs/7 days a week in Chemistry Fast Flow Lab. The test is intended for the benefit of the healthcare worker (employee or student) who has received an accidental stick, cut, or other percutaneous exposure by blood or other infectious fluid or tissue from the “source” patient whose HIV status is unknown. The HIV-Rapid test is performed on a blood sample (lavender top tube) collected from the source patient. The HIV-Rapid test is also performed when ordered by a physician for any age patient in a medical emergency, such as a pregnant woman whose HIV status is not known at the time of delivery. The HIV-Rapid result is critical for prophylactic anti-viral and anti-proteinase therapy which must be initiated within 1-2 hours of the worker’s exposure. Treatment in medical emergencies is similarly time-critical. A positive test HIV-Rapid test must be sent out for Western blot confirmation. No further testing is performed if the source patient’s blood is negative by the Rapid HIV-1 Antibody Test. Call LSS or Client Services for further information. VII. References 1. Moyer TP. Therapeutic Drug Monitoring. Chapter 26. In: Tietz Textbook of Clinical Chemistry, 3rd edition. Burtis CA, Ashwood, EA, eds. 1999: 862-905. 2. Porter WH. Clinical Toxicology. Chapter 27. In: Tietz Textbook of Clinical Chemistry, 3rd edition. Burtis CA, Ashwood, EA, eds. 1999: 906-981. 3. Ellenhorn’s Medical Toxicology, Diagnosis and Treatment of Human Poisoning, 2nd edition, Ellenhorn, MJ. ed. 1998.
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