Reading Assignment PMLS 2 FINALS Lec Exam 1

• PREANALYTICAL CONSIDERATIONS
• KRISTINE ABEGAIL B. ANIÑON, RMT
• PRINCIPLE OF MEDICAL LABORATORY SCIENCE PRACTICE 2
• WEEK 9: PRE-ANALYTICAL COSIDERATIONS IN PHLEBOTOMY
• OBJECTIVES


  • List and describe the physiological variables that influence laboratory test results and identify the tests most affected by each one
  • List problem areas to avoid in site selection, identify causes for concern, and describe procedures to follow when encountering each
  • Identify and describe various vascular access sites and devices and explain what to do when they are encountered
  • Identify, describe, and explain how to handle patient complications associated with blood collection
  • Identify, describe, and explain how to avoid or handle procedural error risks, specimen quality concerns, and reasons for failure to draw blood
• TOPICS


  • PREANALYTICAL
  • REFERENCE RANGES/INTERVALS
  • BASAL STATE
  • PHYSIOLOGICAL VARIABLES
  • VASCULAR ACCESS DEVICES (VADS) AND SITES
  • PATIENT COMPLICATIONS AND CONDITIONS
  • PROCEDURAL ERROR RISKS
  • TROUBLESHOOTING FAILED VENIPUNCTURE
  • SPECIMEN QUALITY CONCERNS
• REFERENCE RANGES/INTERVALS


  Most tests are performed to confirm health or to screen for, diagnose, or monitor disease. To be properly evaluated, test results typically need to be compared with results expected of healthy individuals.
• REFERENCE RANGES/INTERVALS


  One way a physician evaluates a patient's test results is by comparing them to reference ranges and, if applicable, previous results on the same patient. If a specimen has been compromised and the results are not valid, a physician could make a decision based upon incorrect information and thus jeopardize the patient's care.
• BASAL STATE


  Basal state refers to the resting metabolic state of the body early in the morning after fasting for approximately 12 hours. A basal-state specimen is ideal for establishing reference ranges on inpatients because the effects of diet, exercise, and other controllable factors on test results are minimized or eliminated. Basal state is influenced by a number of physiologic patient variables such as age, gender, and conditions of the body that cannot be eliminated. Outpatient specimens are not basal-state specimens and may have slightly different reference ranges (normal values).
• PHYSIOLOGICAL VARIABLES


  • AGE
  • ALTITUDE
  • DEHYDRATION
  • DIET
  • DIURNAL/CIRCADIAN VARIATIONS
  • DRUG THERAPY
  • EXERCISE
  • FEVER
  • GENDER
  • INTRAMUSCULAR REJECTION
  • JAUNDICE
  • POSITION
  • PREGNANCY
  • SMOKING
  • STRESS
  • TEMPERATURE & HUMIDITY
• AGE


  Values for some blood components vary considerably depending upon the age of the patient. For example, red blood cell (RBC) and white blood cell (WBC) values are normally higher in newborns than in adults. Some physiological functions such as kidney function decrease with age. For example, creatinine clearance, a measure of kidney function, is directly related to the age of the patient, which must be factored in when test results are being calculated.
• ALTITUDE


  Decreased oxygen levels at higher altitudes cause the body to produce more RBCs to meet the body's oxygen requirements; the higher the altitude, the greater the increase. Thus RBC counts and related determinations such as hemoglobin (Hgb) and hematocrit (Hct) have higher reference ranges at higher elevations. Other analytes that increase at higher elevations include C-reactive protein and uric acid. Analytes that decrease in value at increased altitude include urinary creatinine (which in turn affects creatinine clearance tests) and plasma renin.

  
• DEHYDRATION


  Dehydration (decrease in total body fluid), which occurs, for example, with persistent vomiting or diarrhea, causes hemoconcentration, a condition in which blood components that cannot easily leave the bloodstream become concentrated in the smaller plasma volume. Blood components affected include RBCs, enzymes, iron (Fe), calcium (Ca), sodium (Na), and coagulation factors.
• DIET


  Requiring a patient to fast or follow a special diet eliminates most dietary influences on test- ing. Patients are typically asked to fast approximately 8 to 12 hours, depending on the test. Fasting is normally done overnight after the last evening meal, with specimens collected the following morning before the patient has eaten.
• DIURNAL/CIRCADIAN VARIATIONS


  The levels of many blood components normally exhibit diurnal (happening daily) or circa- dian (having a 24-hour cycle) variations or fluctuations. Factors that play a role in diurnal variations include posture, activity, eating, daylight and darkness, and being awake or asleep. For example, melatonin levels are affected by light; they increase at night, when it is dark, and decrease during daylight hours. Maximum renin and thyroid-stimulating hormone (TSH) levels normally occur in the predawn hours of the morning during sleep, while peak cortisol levels normally occur later in the morning, around 8:00 A.M. Other blood components that exhibit diurnal variation with highest levels occurring in the morning include aldosterone, bilirubin, cortisol, hemoglobin, insulin, iron, potassium, testosterone, and RBCs. Blood levels of eosinophils, creatinine, glucose, growth hormone (GH), triglycerides, and phosphate are normally lowest in the morning. Diurnal variations can be large. For example the levels of cortisol, TSH, and iron can differ by 50% or more between morning and late afternoon.