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Introduction to Laboratory Medicine

Introduction to Laboratory Medicine. Roger L. Bertholf, Ph.D. Some SHJ Lab Statistics. Number of employees: 130 Number of tests/year: 1.5 million Yearly budget: $16 million Yearly revenue: $70 million Net $25 million. Laboratory organization. Core Laboratory (73% of volume)

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Introduction to Laboratory Medicine

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  1. Introduction to Laboratory Medicine Roger L. Bertholf, Ph.D.

  2. Some SHJ Lab Statistics • Number of employees: 130 • Number of tests/year: 1.5 million • Yearly budget: $16 million • Yearly revenue: $70 million • Net $25 million

  3. Laboratory organization • Core Laboratory (73% of volume) • Chemistry, hematology, toxicology, immuno-chemistry, special chemistry, coagulation, urinalysis • Microbiology (16 % of volume) • Blood/urine cultures, serology • Transfusion Services (3% of volume) • Blood typing and cross-matching

  4. Chemistry • Electrolytes, glu, BUN, creat, phos, TP, Bili, Mg, Ca, cholesterol, triglycerides, etc. • Blood gases: pO2, pCO2, pH, calc. Parameters • Immunochemistry: endocrine, specific protein, tumor markers • Toxicology: DAU, TDM • Urinalysis • Special Chemistry: electrophoresis, L/S ratio, FLM, osmometry

  5. SHJ Chemistry Instruments • Roche/Hitachi Modular and 914 • Chemistries and homogeneous immunoassays • Roche Elecsys 2010 • Heterogeneous immunoassays • NOVA M (whole blood gas/electrolytes) • Abbott IMx • Yellow Iris

  6. Hematology • CBC/Diff • Coagulation • Microscopy

  7. SHJ Hematology Instruments • Abbott Cell Dyne 4000 • CBC, Auto differential • Organon Technika MDA • Coagulation

  8. Microbiology • Cultures • Blood • Urine • Sputum, wound, etc. • Antibiotic sensitivity • Serology • Viral Ab, Ag testing

  9. Point of Care Testing • Instruments are available that can perform certain tests at remote locations, such as at the bedside on in a clinical care unit • Blood glucose • Urinalysis • Blood gases • Electrolytes/BUN/Creatinine • Cardiac markers (Troponin I & T, CK-MB) • Coagulation (ACT) • POC tests are nearly always more expensive, than the same tests performed in the central laboratory

  10. POCT at SHJ • Blood glucose (Not under lab license) • Electrolytes on the GEM Premier in the OR • ACT in the OR and Cardiac Catheterization Lab • Urinalysis (not under lab license)

  11. Reasons for POC testing • Tests are of urgent importance, and results will affect the immediate management of the patient • Blood gases, electrolytes • Tests are so common, simple and cheap that it is more economical to perform them at the point of care • Blood glucose, urinalysis

  12. SHJ Blood Gas Lab • Operated by Respiratory Therapy • Performs blood gases and whole blood electrolytes/BUN/Creatinine/Glucose • Gases fall under RT license • Chemistries fall under the lab license • Serves MICU, CCU, PICU, NICU, SICU • Performs all co-oximetry

  13. Steps in obtaining a laboratory test • Written order is placed • Specimen is collected and properly labeled • Specimen and order are transported to the lab • The specimen is accessioned in the lab • The specimen is processed • The specimen is analyzed • The results are reviewed and verified by an MT • The results are released to the patient’s record

  14. How long steps 4-7 take (P1 orders)

  15. How long steps 4-7 take (STAT)

  16. Sources of error in laboratory results • Pre-analytical • Analytical • Post-analytical

  17. Pre-analytical errors • Collection • Was the right tube used? • Was venipuncture performed correctly? • Was the specimen properly stored? • Identification • Was the blood collected from the correct patient? • Was the blood correctly labeled? • Patient name, ID, date, time of collection, phlebotomist

  18. Collection tubes • Red-top tubes contain no anticoagulants or preservatives • Red-top tubes are used for collecting serum • 10-15 minutes is required to allow blood to clot before centrifuging • Used for blood bank specimens, some chemistries

  19. Collection tubes • Gold (and “tiger”) top tubes contain a gel that forms a physical barrier between the serum and cells after centrifugation • No other additives are present • Gel barrier may affect some lab tests

  20. Collection tubes • Gray-top tubes contain either: • Sodium fluoride and potassium oxalate, or • Sodium iodoacetate • Both perservatives stabilize glucose in plasma • NaF/oxalate inhibits enolase • Iodoacetate inhibits glucose-3-phosphate dehydrogenase

  21. Collection tubes • Green-top tubes contain either the sodium or lithium salt of heparin • The amount of Na+ or Li+ is insignificant • Heparin inhibits thrombin, so blood does not clot (plasma) • The advantage of plasma is that no time is wasted waiting for the specimen to clot

  22. Collection tubes • Lavender-top tubes contain EDTA, which chelates calcium and inhibits coagulation • Used for hematology, and some chemistries

  23. Collection tubes • Blue-top tubes contain sodium citrate, which chelates calcium and inhibits coagulation • The blood/anticoagulant ratio must be precisely known, since the tubes are used for coagulation studies.

  24. Collection tubes • Brown and Royal Blue top tubes are specially cleaned for trace metal studies • Brown-top tubes are used for Pb analysis • Royal blue-top tubes are used for other trace element studies (acid washed)

  25. Plasma/Serum differences • Plasma concentration greater than serum: • Ca (+0.9%), LD (+2.7%), TP (+4.0%) • Plasma concentration less than serum: • Alb (-1.3%), ALKP (-1.6%), HCO3- (-1.8%), CK (-2.1%), PO4= (-7.0%), K+ (-8.4%)

  26. Prolonged venous stasis • Increases TP, Fe, cholesterol, AST, bilirubin • Decreases potassium

  27. Supine vs. sitting or standing • The following may decrease by 5-15% in the supine patient: • Total protein • Albumin • Lipids • Iron • Calcium • Enzymes • Ig • Thyroxine

  28. Significantly affected by hemolysis: • Total protein, albumin, lipids, iron, calcium, enzymes, bilirubn, cholesterol, triglycerides, norepinephrine, renin, aldosterone, potassium, magnesium, phosphorous

  29. Specimens requiring special handling • Should be placed immediately on ice • Lactate • Ammonia • Acid phosphatase • Plasma catecholamines

  30. Exertion-related changes • Recent strenuous exercise increases: • Acid phosphatase, ALT, AST, creatinine, phosphorous, CK • Recent strenuous exercise decreases: • Iron, lipids, potassium

  31. Other factors affecting lab results • Diurnal variations • Cortisol, iron, estriol, glucose, catecholamines • Age • Creatinine, BUN, ALKP, drug metabolism • Smoking • Ammonia, CO-Hb

  32. Specimen identification • One of the commonest sources of erroneous lab results is misidentified specimens • CAP and other accrediting agencies require the lab to have a clear and rational policy for identifying specimens, and handling misidentified specimens • The blood bank has stricter requirements for specimen identification

  33. Misidentified specimens at SHJ 29: Delay in obtaining lab results 26: Specimen collected/labeled/registered with wrong patient 46: Specimen unlabeled/mislabeled/labeled incompletely

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