PMLS 2 LEC MODULE 6 UNIT 5

• Point-of-care testing (POCT)


  Also known as alternate site testing (AST), ancillary or bedside-patient testing wherein blood is collected and laboratory testing is done at bedside or near the patient
• POCT instruments


  • Small, portable, and easily carried and handheld
• Benefits of POCT


  Convenience to the patient and a short turnaround time for results that allow healthcare providers to address crucial patient needs, deliver prompt medical attention and expedite patient recovery
• In clinical settings, it is necessary to follow the requirements of the Clinical Laboratory Improvement Amendments (CLIA) for testing and the guidelines of the Occupational Safety and Health Administration (OSHA) for specimen handling
• Performing POCT


  1. Do quality-control (QC) and maintenance procedures

  2. Possess phlebotomy skills required to collect the specimen

  3. Operate the laboratory instrument according to the manufacturer's instructions
• Disinfectant for POCT instruments

  10% bleach, prepared and mixed daily
• Quality control for POCT

  1. All control results must be recorded on a QC log and reviewed for consistency and acceptability

  2. For non-instrumented tests, daily external liquid QC must be performed as a check on the technique used and the accuracy of the results
• Non-instrumented POCT


  Tests that do not use instruments, such as urine dipsticks that are read visually
• Monitored POCT coagulation tests

  • Activated partial thromboplastin time (APTT or PTT)
  • Prothrombin time (PT) and international normalized ratio (INR)
  • Activated clotting time (ACT)
  • Platelet function
• Activated Clotting Time (ACT)


  Analyzes the activity of the intrinsic coagulation factors and used to monitor heparin therapy
• Prothrombin Time and International Normalized Ratio (PT/INR)


  Used to monitor warfarin therapy
• Activated Partial Thromboplastin Time (APTT/PTT)


  Used to screen for bleeding disorders prior to surgery, investigate bleeding or clotting disorders, detect clotting factor deficiencies, and monitor low-dose heparin therapy
• Platelet Function


  Determines patient's response to antiplatelet medication before open heart surgery or cardiac catheterization
• POCT instruments for coagulation tests

  • Cascade POC (ACT, APTT, PT/INR)
  • CoaguChek XS Plus (PT/INR)
  • GEM Premier 4000 (ACT, APTT, PT/INR)
  • i-STAT (ACT, PT/INR)
  • Verify Now (Platelet function)
• Bleeding-time (BT) test


  Evaluates platelet plug formation in the capillaries to detect platelet function disorders and capillary integrity problems
• Equipment needed for BT test

  • Blood pressure cuff
  • Sterile automated incision device (e.g., Surgicutt)
  • Stopwatch or any timing device
  • Alcohol, cotton balls, and micropore (suitable skin antiseptic)

  
• Ingestion of aspirin or other salicylate-containing drugs or drugs such as ethanol, dextran, and streptokinase within 2 weeks of the BT test can abnormally prolong bleeding time
• Any disturbance of platelet plug formation will increase the bleeding time
• BP below or above 40 mm Hg will decrease or increase the bleeding time, respectively
• Failure to start the timing as soon as the incision is made will decrease the bleeding time
• Too little pressure on the incision device will decrease, and too much pressure will increase the bleeding time

  
• Arterial Blood Gases (ABGs)


  POCT is extremely useful in critical care settings, where both arterial blood gases and electrolytes must be maintained
• Bleeding time


  Time taken for bleeding to stop after an incision is made
• Drugs like ethanol, dextran, and streptokinase within 2 weeks of the test


  Can abnormally prolong bleeding time
• Any disturbance of platelet plug formation

  Will increase the bleeding time
• BP below 40 mm Hg

  Will decrease the bleeding time
• BP above 40 mm Hg


  Will increase the bleeding time
• Failure to start the timing as soon as the incision is made

  Will decrease the bleeding time
• Too little pressure on the incision device

  Will decrease the bleeding time
• Too much pressure on the incision device

  Will increase the bleeding time
• POCT


  Point-of-care testing, extremely useful in critical care settings
• Arterial blood gases (ABGs)

  Tests used to determine the pH of blood
• pH


  A scale representing the relative acidity or alkalinity of a solution
• pH


  • Measure of the body's acid-base balance, indicates metabolic and respiratory state
  • Normal value: 7.35-7.45
  • Acidosis: <7.35
  • Alkalosis: >7.45
• Partial pressure of carbon dioxide (pCO2)


  Measure of the pressure exerted by dissolved CO2 in the blood plasma, proportional to the PCO2 in the alveoli
• pCO2


  • Abnormal increase = Hypoventilation
  • Abnormal decrease = Hyperventilation
  • Indicator of how well air is being exchanged between the blood and the lungs
• Partial pressure of oxygen (pO2)

  Measure of the pressure exerted by dissolved O2 in the blood plasma, indicates the ability of the lungs to diffuse Oxygen (O2) through the alveoli into the blood
• Oxygen saturation (sO2)


  Measure of the percentage of hemoglobin binding sites occupied by oxygen in the bloodstream
• sO2


  • Normal value: 98%
  • Hypoxemia (low oxygen): <90%
  • Determines a patient's oxygenation status
• Electrolytes must be balanced to maintain the normal function of cells and organs