Medical Technology Notes

Chain of Custody

  • Definition from Henry's, a comprehensive book for medical technologists.
  • Applies to various samples, not just urine.
  • Involves a chain of designated individuals:
    • Person collecting the sample.
    • Designated individual (e.g., police officer) transporting the sample to the lab.
    • Witness to testing or assigned individuals performing the testing.
  • Important in legal matters like paternity testing.
  • Acceptable samples: blood, cheek swabs.

Therapeutic Drug Monitoring

  • Analyzing drug levels in the bloodstream to maintain dosage, especially for therapeutic reasons.
  • Timing of specimen collection is crucial due to the "kickoff effect" (peak drug effectiveness).
  • Aims to identify therapeutic levels and avoid drug toxicity.
  • Coordination between pharmacists, nurses, and the lab.
  • Collection often occurs at peak level to assess maximum levels and trough level to see if drug maintains therapeutic ability.
  • Categories of drugs requiring monitoring (not necessary to memorize).

Therapeutic Phlebotomy

  • Withdrawal of a large amount of blood (450-500 mL) that is then discarded.
  • Performed for conditions like:
    • Polycythemia vera: Overproduction of RBCs, leading to excessive hematocrit and hemoglobin (harmful).
    • Hemochromatosis: Iron overload, where excess iron is stored in organs like the liver and pancreas.

Toxicology Specimens

  • Two types:
    • Forensic specimens: Required by law enforcement to identify the presence of alcohol (breath or blood) or drugs (urine or blood).
    • Drug screening: Required by healthcare organizations, sports associations, and companies (random, pre-employment, post-accident).
  • Both types require a proper chain of custody.
  • Drug screenings typically screen for 30 drugs in urine.

Drug Screening

  • Detects illegal drugs such as amphetamines and cannabinoids.
  • Detectable time window varies by drug (e.g., marijuana: 1-2 days, metabolites up to 7 days; methamphetamine: 1-3 days).
  • Patient preparation:
    • Explain the test purpose and procedure.
    • Advise on legal rights.
    • Obtain witness or consent form.
  • Specimen collected in a special area for urine collection.
  • Special considerations for urine collection:
    • No running water (to prevent dilution).
    • Inspection and provision of a container.
    • Proctor in a special area.
    • Specimen must be labeled, sealed, and placed in container.
  • Medical technologists in the Philippines require certification to perform drug screening.
  • Screening tests are followed by confirmatory testing if positive.

Trace Elements

  • Looking for elements like aluminium, arsenic, copper, lead, and iron for poisoning reasons.
  • Requires special evacuated tubes (royal blue) containing EDTA, sodium heparin, or no additive.

Point of Care Testing (POCT)

  • Also known as alternative site testing, ancillary, bedside, or near-patient testing.
  • Performed near the patient; no need to transport samples to the laboratory.
  • Requires small, portable, often handheld machines.
  • Example: Glucose testing.
  • Advantages: Convenient, short turnaround time, no need for large laboratories or specimen transportation.
  • Phlebotomists need to be informed about POCT.

POCT Quality Control

  • Ensures accurate and precise results within reference ranges.
  • Regulations evolve periodically.
  • Two types of tests:
    • Waived tests: Do not require the same level of quality checks as non-waived tests.
    • Non-waived tests: Most POCT are non-waived due to the complexity of the machine is lower than the laboratory machines.
  • POCT principles and complexity are less than larger laboratory machines.
  • Limitations: Not used as a confirmatory test but for monitoring; has more limitations compared to complex machines.
  • External QC can be performed to identify if the machine is up to par.
  • Liquid controls are performed upon receiving new test kits.
  • Some POCT tickets have internal QC checks to detect specimen issues.
  • QC log: Contains samples (normal, abnormal, and midrange) provided by manufacturers or institutions like RITM (external quality control).

Infection Control

  • POCT machines can cause contamination from one room to another.
  • Fomites: Any objects capable of carrying infectious agents (e.g., tourniquets, POCT trays).
  • Institutions like CDC and HCPAP regulate rules.
  • Maintain proper cleaning and handling of POCT machines.
  • Recommended: 10% bleach solution to reduce cross-contamination.

POCT Coagulation Monitoring

  • Used to monitor patients on warfarin and heparin therapy.
  • Tests performed: PT, APTT, INR, ACT, and platelet function.
  • Activated Clotting Time (ACT): Measures intrinsic coagulation factor capability to clot blood and monitors heparin therapy.
  • Prothrombin Time (PT): Monitors warfarin and measures how long blood takes to clot.
  • Platelet Function Testing: Evaluates patient's response to antiplatelet medications before open heart surgery or cardiac catheterization to ensure no bleeding tendencies or clotting issues.
  • Technique: Cartridge is inserted into the machine.
  • Bleeding time test is technique-dependent and considered error-prone.

Arterial Blood Gas (ABG)

  • I-STAT machine is often used.
  • Key points:
    • Ensure no bubbles in the sample, as they invalidate the test.
    • Assess if the sample is arterial or venous, as venous samples can lead to misdiagnosis.
    • Skills: Learning to dispense the sample properly and assess the sample type.
  • Parameters Measured:
    • pH: Normal range is 7.35−7.457.35 - 7.45. Increased pH indicates alkalosis, and decreased pH indicates acidosis.
    • PCO2: Partial pressure of carbon dioxide indicating air exchange between blood and lungs.
    • PO2: Partial pressure of oxygen indicating the ability of lungs to diffuse oxygen through the alveoli into blood.
    • SO2: Oxygen saturation, measuring the percentage of hemoglobin binding sites filled with oxygen; oxygen attaches to hemoglobin in red cells.
  • Used in emergency situations; reliable for some institutions.

Electrolytes

  • Carry electrical impulses across cell membranes.
  • Crucial for heart, nerve, and muscle function.
  • Common electrolytes: sodium, potassium, chloride, bicarbonate, and ionized calcium.
    • Sodium: Most plentiful electrolyte in the blood, maintaining osmotic pressure, acid-base balance, and nerve impulse transmission.
    • Potassium: Primarily intracellular; released when cells are damaged (hemolyzed); essential for nerve conduction, muscle function, acid-base balance, osmotic pressure, and kidney-related functions.
    • Chloride: Plays a role in fluid and pH balance.
    • Bicarbonate ion
    • Ionized calcium

Multiple Test Panel Monitoring by POCT

  • Capable of measuring multiple parameters (electrolytes, blood gases, other analytes like BUN, glucose, hemoglobin, hematocrit).

B-Type Natriuretic Peptide (BNP)

  • Cardiac hormone responding to ventricular volume expansion and pressure overload.
  • Used to measure the existence of congestive heart failure (CHF).
  • Differentiates between chronic obstructive pulmonary disease (COPD) and CHF.
  • i-STAT system is an example.
  • Process: Open the circular part to put blood samples, then close it. The results will be invalidated, if there is any gap.

Bilirubin Testing

  • Philips Healthcare BiliCheck Analyzer (non-invasive).
  • Meter directs light into the skin, measuring reflected wavelengths to identify bilirubin concentration without blood collection.
  • Helpful for newborns prone to jaundice.
  • Measures the wavelengths that are reflected back.

Cardiac Troponin T and I (cTnT and cTnI)

  • Specific proteins related to heart muscles.
  • Viable tools for acute myocardial infarction (AMI) or heart attack.
  • Differentiates between CHF (high in BNP) and AMI (high in cTnT and cTnI).
  • cTnT rises within 4 hours of myocardial damage.
  • cTnI detected within 3-6 hours; normalizes within 5-10 days.
  • Examples: Cardiac T Rapid Assay and Triage Cardiac Panel.

Complete Blood Count (CBC)

  • Sysmex Ruby is a famous machine brand.
  • Compact version compared to complex laboratory parameters.
  • Allows immediate medical intervention.
  • Assesses basic parameters: RBC, hemoglobin, hematocrit, WBC, and differential counts.
  • Provides same-day results in doctor's offices and clinics.

C-Reactive Protein (CRP)

  • Inflammation or infection marker that elevate when an inflammation or infection happens.
  • Made by the liver and released upon tissue injury or infection.
  • Sensitive but non-specific marker (does not pinpoint the cause of inflammation or infection).
  • Examples: Gp and Onefold machines.
  • For GP, there are manipulation to specific kit.
  • Can only detect specific range of values.

Glucose

  • Most common procedure for monitoring diabetes.
  • Whole blood specimens obtained via skin puncture.
  • Stored strips must be tightly recapped; humidity can affect test strips.
  • Tapooyari specimens aren't true representation glucose concentration.
  • Useful for monitoring.

Glycohemoglobin or Hemoglobin A1c (HbA1c)

  • HbA1c is a type of hemoglobin found in normal, healthy adults.
  • Detects glucose that remains attached to hemoglobin and its RBC; RBCs have a 120-day lifespan.
  • Detects glucose level for the past 2-3 months, making it difficult to manipulate or "cheat".
  • Provides a comprehensive/average level of glucose over time and gives insight to the patient's lifestyle/diet.
  • Used with other glucose level tests (fasting sugar) to predict the likelihood of diabetes.

Hematocrit

  • Measure the volume of RBC.
  • Special capillary tubes are used, sealed, and centrifuged.
  • A specialized ruler measures hematocrit.
  • Air gaps should be avoided.

Hemoglobin

  • Measures hemoglobin levels to manage patients with anemia.
  • A small amount of blood is placed in a special cuvette and inserted into the machine for reading.

Lactate

  • Monitors metabolic issues resulting from hyperlactemia (common in severe sepsis or septic shock).
  • The increased bacteria consumes nutrients from blood to create an acidic environment, which may cause lactic acidosis.
  • Marker for severity of patients in stress response situations.

Lipid/Cholesterol Testing

  • Lipids fat based substances (cholesterol and triglycerides).
  • High-density lipoprotein (HDL) is “good” cholesterol while low-density lipoprotein (LDL) is “bad” cholesterol.
  • Total cholesterol is one of the parameters as well to diagnose.
  • Diagnosis needs a ten to twelve hours of fasting.

Rapid Syphilis Test

  • Detects antibodies, not the bacteria.
  • Caused by the bacteria Treponema pallidum.
  • Antibodies are produced in response to this bacteria.
  • A buffer (reagent) is mixed with the blood (serum, plasma, or whole blood).
  • Results available within 15 minutes.
  • Screening test requires confirmatory testing (nucleic acid amplification testing) for the positive results.