introduction to the principles of laboratory medicine

Introduction to the Principles of Laboratory

Medicine

Module 1What is laboratory medicine?

Case Scenario 1 O A 77-year old man presents to the

emergency department with fevers and chills. He has had multiple urinary tract infections in the past and feels that this is “another one”. He has a history of diabetes mellitus, type 2 with diabetic nephropathy and chronic kidney disease. Physical exam is notable for an ill-appearing man with right flank tenderness.

O How will the medical laboratory impact this patient’s care?

Case Scenario 1Discussion

O Confirm clinical diagnosisO Urinalysis

O Guide appropriate dosing of antibioticsO Dose adjustment for reduced GFR

based on variables including serum creatinine

O Guide selection of appropriate antibiotic therapyO With multiple course of treatment in

the past there may be issues with antibiotic resistance

Photo by Elizabeth Wantuch, MD

Call “the lab”….O Today’s clinical laboratory is a

complex arena offering an expansive menu of tests which continues to grow

O Hundreds of millions of laboratory tests are performed every year in the United States

Influence of Laboratory Medicine on the quality and cost of

healthcareO Lab tests consume about 2.3% of

annual health care costs in the United States

O It is noted in the literature that >70% of the objective data in a patient’s medical record comes from the clinical laboratory

WHAT is “Laboratory Medicine”?O Laboratory medicine (clinical

pathology) is the medical discipline that specializes in the performance, reporting and interpretation of clinical laboratory tests in the provision of high quality patient care

WHO is “Laboratory Medicine”O Comprised of pathologists, doctoral-

level laboratory scientists, technologists, and technicians

O The laboratory medicine workforce has a vital role in the health care system managing and applying evidence-based, scientific testing techniques to support patient care

The specific types of clinical laboratories in health care institutions varies greatly from one place to another.

Listed below is a partial list of types of individual clinical

laboratories

OBlood Bank/ApheresisOChemistry/ImmunoassayOHematology and CoagulationOUrinalysis, Fluid Analysis and Medical MicroscopyOCytogeneticsOEndocrinologyOImmunoserologyOMicrobiology (including Bacteriology, Virology, Parasitology, etc.)OMolecular PathologyOTissue Typing/HLAOToxicology

O Each lab may have one medical director and one technical specialist responsible for testing services and quality of the lab

O Some labs require a combined leadership group of 2-3 directors and multiple technical specialists

Additional Terms

Photo by Theresa Kristopaitis, MD

“Reference lab”

O In our medical center the lab tests performed at reference labs are often called “send out labs”

OClinical reference laboratories provide testing services for patients and healthcare providersOThe labs performed are generally specialized tests that are infrequently ordered or that require specialized equipment

“Point of Care Testing”

Photo by Theresa Kristopaitis, MD

Point of Care Testing (POCT) is laboratory testing performed on simpler devices at the point of care (e.g., the bedside) and often by non-laboratory personnel

Case Scenario 2O A 5-year old boy is at his physician’s office

with fever, sore throat and severe pain with swallowing x 2 days. On physical exam his temperature is 390C. There is tonsillar erythema and swelling with white exudates.

O What point of care test do you think was performed?O A rapid Streptococcal antigen test

O The test is positive. How does this impact the care of the patient?O Appropriate antibiotics are prescribed

O What if the test were negative?O The physician understands the sensitivity

and predictive value of the rapid antigen test. If the clinical suspicion for Streptococcal pharyngitis is high a throat culture would be submitted

Case Scenario 3O A 5-year old boy is at his physician’s office

with low grade fevers, sore throat, runny nose, watery eyes for the past week. On physical exam he is afebrile. There is minimal tonsillar swelling and erythema without exudates. The boy’s parents insist that he be treated with antibiotics.

O The physician has a low clinical suspicion for Streptococcal pharyngitis but does perform a POCT Strep antigen screen. The result is negative. How does this impact patient care?O Support to not provide unnecessary

antibiotic therapy for what is likely a viral upper respiratory tract infection

What is the Point of “POCT”?

O The key objective of POCT is to produce a result more quicklyO Therefore the utility of POCT is in the

immediacy of response and effect on medical decision making

O Due to advances in technology, clinical needs and a number of other factors, POCT may be the most rapidly growing segment of laboratory testing worldwide

What POCT is available for the following patients?

O 24-year old woman with amenorrhea x 2 months?O Urine HCG

O 42-year old man with diabetes mellitus?O Glucose, HgbA1c, urine microalbumin

O 63-year old woman with atrial fibrillation on warfarinO INR

O 78-year old man presenting to the ED with 10/10 crushing chest painO Troponin

O Proceed to “Module 2: The Diagnostic Testing Process”