Beth Israel Deaconess Medical Center Laboratory Manual

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Oct. 2003 - Tumor Marker Considerations

July 2003 - New Method for Troponins Begins on July 1, 2003

July 2003 - Reference Range Upate for Many Tests on July 1, 2003

March 2003 - Integrated Modular Analytics Analyzer goes live - click here for details of the changes

Clinical Chemistry is a comprehensive laboratory, performing well over one hundred different assays using a wide variety of different techniques. The laboratory includes work areas dedicated to blood gas (and other whole blood) analysis; highly automated spectrophotometry, allowing for the simultaneous quantitation of dozens of chemical constituents of blood; therapeutic drug monitoring and toxicology; automated immunoassays for endocrinology, tumor markers, and other low concentration analytes; protein electrophoresis and immunofixation electrophoresis; immunoassays for hepatitis and related serologies; prenatal screening; and fetal lung maturity testing.

Testing includes 24-hour availability of a wide variety of analytes, such as metabolites (glucose, electrolytes, urea, creatinine, bilirubin, calcium, iron, magnesium, and uric acid); lipid parameters (triglyceride, total cholesterol, and HDL cholesterol); enzymes (ALT, alkaline phosphatase, amylase, AST, CK, LD, and lipase); and proteins (total protein, albumin, transferrin, CSF and urine protein). Results are usually available within 3-4 hours of receipt. Thus, for in-patients, results for almost all routine chemistry tests drawn during morning rounds will be available before noon. Please note that all testing is discrete:  our instruments will run (and we will report) those tests and only those tests that you order.

Clinical Chemistry Immunology services include immunochemical analyses of abnormal immunoglobulins in serum, urine, and body fluid; autoantibodies; complement testing, as well as the serologic diagnosis of infectious disease. The Immunoassay section offers comprehensive testing for hormone, proteins, and tumor antigens. Most of the tests are performed daily (see details under specific test).

Blood gas results (pO 2, pCO2 , pH) are usually available within 5-10 minutes of receipt of a properly drawn 1 ml specimen. It is particularly important to draw the samples properly. For example, dilution of the specimen with anticoagulant, whether from an indwelling line or from the particular blood drawing set used, will cause erroneous pH and pCO2 measurements; insufficient anticoagulant or inadequate mixing will cause the specimen to clot, in which case it cannot be analyzed as it will damage the lab's instrumentation. In emergency situations, the same specimen can be used for whole blood Na/K analysis. The blood gas analyzers also measure whole blood lactate, glucose, chloride, and ionized calcium.

We offer a large repertoire of in-house testing, including anticonvulsants (carbamazepine, phenobarbital, phenytoin, valproic acid), cardioactive drugs (digoxin, procainamide, quinidine), antibiotics (gentamicin, tobramycin, vancomycin), transplant-related drugs (cyclosporine, FK506 [tacrolimus], rapamycin).

It is important to point out that timing is critical in interpreting drug levels. If the specimen is drawn without careful attention to the time of administration, the result probably will be uninterpretable. In general, for oral drugs, the appropriate time to draw specimens is after 5 half lives of administration of a constant dose and just before the next dose (a "trough"). More precise data regarding pharmacokinetic analysis is available through the laboratory by request.

At Beth Israel Deaconess Medical Center, we use immunoassays to screen for the presence of drugs in blood and/or urine. In some cases, the assays detect many members of the same class of drugs and the screen is reported either as "positive" or "negative". Other assays (acetaminophen, ethanol, salicylates) are specific for one drug, and the result will be reported quantitatively.

If you have questions about cross-reactivities, cut-offs used for specific assays, or whether specific drugs will be detected, page the Laboratory Director on-call.

Legal issues: Pre-employment "drugs of abuse" testing is not performed in the Beth Israel Deaconess Medical Center Clinical Laboratory. Informed consent, if required, is the responsibility of the ordering physician. Formal chain-of-custody documentation is not practiced routinely at Beth Israel Deaconess Medical Center.

• Indicate which drugs you suspect.
• Submit both blood and urine. (Some drugs are detected only in urine, others are detected only in blood. If you submit just one fluid, you will miss some important drugs.)
• For drugs whose absorption might be delayed, get a second serum specimen 2-3 hours later. (Such drugs include acetaminophen, salicylate, tricyclic antidepressants.)
• Anticonvulsants are not included in the drug screens. These must be added separately.
• Many drugs are not routinely detected by our toxic screen.

If you suspect any clinically significant discrepancy between the toxic screen results and your patient's condition (or have any questions about the program), page the Laboratory Director on-call. In general, if necessary, blood and urine specimens can be referred to an off-site laboratory to detect other compounds or to identify specific drugs not detected in our screening assays. In addition, we can provide you with some strategies for dealing with these situations.

Revised/reviewed 4/11/2008