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 7.35−7.45. 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.