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Solving Puzzles of Laboratory Data Interpretation

Solving Puzzles of Laboratory Data Interpretation. Evaluation of Visceral Protein Status. Affected by numerous other factors, including hydration status, chronic illness, acute phase response May have low sensitivity/specificity

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Solving Puzzles of Laboratory Data Interpretation

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  1. Solving Puzzles of Laboratory Data Interpretation

  2. Evaluation of Visceral Protein Status • Affected by numerous other factors, including hydration status, chronic illness, acute phase response • May have low sensitivity/specificity • However, low serum albumin and acute phase proteins are associated with increased complications and length of stay in hospitalized patients; probably an index of severity of illness

  3. Preoperative Albumin as a Predictor of Risk in Elective Surgery Patients • Retrospective review of 520 patients with preoperative serum albumin measurements • Preoperative albumin correlated inversely with complications, length of stay, postoperative stay, ICU stay, mortality, and resumption of oral intake • S. albumin levels <3.2 were predictive of risk • Kudsk et al, JPEN, 2003

  4. Role of Visceral Protein Measurement in Nutrition Screening and Assessment • Low values in critically ill patients a measure of severity of illness • Is a valuable predictor of morbidity/mortality in hospitalized and LTC patients • Can be used to identify elective surgery patients who could benefit from nutrition intervention • Sequential measurements may reflect changes/improvement of nutritional status

  5. Serum Albumin • Normal: 3.5-5.0 g/dL • Half-life approximately 14-20 days • Decreased by: APR (in inflammation, infection, injury, surgery, cancer); severe liver failure, redistribution, intravascular volume overload, third spacing, pregnancy; losses in nephrotic syndrome, burns, protein losing enteropathies, exudates • Increased by: intravascular volume depletion, intravenous albumin or plasminate, anabolic steroids

  6. Serum Transferrin • Normal: 200-400 mg/dL • Half-life: approximately 8-10 days • Decreased by: APR, chronic or end-stage liver disease, uremia, protein-losing states, intravascular volume overload, high-dose antibiotic tx, iron overload, severe zinc deficiency, PCM • Increased by: iron deficiency, chronic blood loss, pregnancy, intravasclar volume depletion, acute hepatitis, oral contraceptives, estrogen

  7. Prealbumin (transthyretin, Thyroxin-Binding Prealbumin) • Normal: 16-40 mg/dL • Half-life: 2-3 days • Decreased by: APR, end stage liver disease, untreated hyperthyroidism, nephrotic syndrome, severe zinc deficiency • Increased by: moderate increase in acute or chronic renal failure, anabolic steroids, possibly glucocorticoids

  8. Retinol-Binding Protein • Normal: 2.7-7.6 mg/dL • Half-life: approximately 12 hours • Decreased by: hyperthyroidism, chronic liver disorders, APR, cystic fibrosis, vitamin A or severe zinc deficiency • Increased by renal failure, glucocorticoids, acute or early liver damage

  9. C-Reactive Protein (CRP) • Monitors the presence, intensity, and recovery from an inflammatory process • Good indicator of the APR and sensitive for diagnosing infection • Not useful as a nutritional marker, however can be used to evaluate effect of APR on nutritional markers such as visceral proteins

  10. CRP • Normal: <0.8 mg/dL (<8 mg/L) • Rises within hours of an acute stimulus • Decrease in CRP of >50 mg/L between admission and day 4 is a good predictor of recovery • As the ACP wanes, expect to see CRP decline • As CRP declines, sensitive visceral proteins should increase

  11. Lipoprotein Profile • Measures total cholesterol, LDL-cholesterol, HDL-cholesterol, and triglycerides • 8-12 hour fast allows chylomicrons to clear • Friedenwald formula for calculating LDL-C = (TC) – (HDL-C) – (TG/5)

  12. Lipoprotein Profile Confounders • Lipids decline significantly 24 hours after an acute MI or other event • Lipid profiles should be done either within 24 hours of an acute myocardial event or several weeks out • Lipids measured after major surgery will be artificially low • Very low total cholesterol may indicate malnutrition • Estrogen decreases serum cholesterol; pregnancy and menopause increase serum cholesterol

  13. ATP III Screening Guidelines New Recommendation for Screening/Detection • Complete lipoprotein profile preferred • Fasting total cholesterol, LDL, HDL, triglycerides • Secondary option • Non-fasting total cholesterol and HDL • Proceed to lipoprotein profile if TC 200 mg/dL or HDL <40 mg/dL

  14. Risk Category CHD and CHD riskequivalents Multiple (2+) risk factors Zero to one risk factor LDL Goal (mg/dL) <100 <130 <160 Three Categories of Risk that Modify LDL-Cholesterol Goals

  15. Major Risk Factors for CHD • Cigarette smoking • Hypertension (BP >140/90 mmHg or on antihypertensive medication) • Low HDL cholesterol (<40 mg/dL) • Family history of premature CHD (CHD in male first degree relative <55 years; • CHD in female first degree relative <65 years) • Age (men >45 years; women >55 years)

  16. CHD Risk Equivalents • Clinical CHD • Symptomatic carotid artery disease • Peripheral arterial disease • Abdominal aortic aneurysm. • Diabetes

  17. ATP III Lipid and Lipoprotein Classification LDL Cholesterol (mg/dL) <100 Optimal 100–129 Near optimal/above optimal 130–159 Borderline high 160–189 High 190 Very high

  18. ATP III Lipid and Lipoprotein Classification (continued) HDL Cholesterol (mg/dL) <40 Low 60 High

  19. ATP III Lipid and Lipoprotein Classification (continued) Total Cholesterol (mg/dL) <200 Desirable 200–239 Borderline high 240 High

  20. Specific Dyslipidemias: Elevated Triglycerides Classification of Serum Triglycerides • Normal <150 mg/dL • Borderline high 150–199 mg/dL • High 200–499 mg/dL • Very high 500 mg/dL

  21. Causes of High Triglycerides(150 mg/dL) • Obesity and overweight • Physical inactivity • Cigarette smoking • Excess alcohol intake

  22. Causes of High Triglycerides • High carbohydrate diets (>60% of energy intake) • Several diseases (type 2 diabetes, chronic renal failure, nephrotic syndrome) • Certain drugs (corticosteroids, estrogens, retinoids, higher doses of beta-blockers) • Various genetic dyslipidemias

  23. Elevated Triglycerides Non-HDL Cholesterol: Secondary Target • Primary target of therapy: LDL cholesterol • Achieve LDL goal before treating non-HDL cholesterol • Therapeutic approaches to elevated non-HDL cholesterol

  24. Non-HDL Cholesterol • Secondary target of therapy when serum triglycerides are 200 mg/dL (esp. 200–499 mg/dL) • Non-HDL cholesterol = VLDL + LDL cholesterol= (Total Cholesterol – HDL cholesterol • Non-HDL cholesterol goal: LDL-cholesterol goal + 30 mg/dL)

  25. Comparison of LDL Cholesterol and Non-HDL Cholesterol Goals forThree Risk Categories Risk Category LDL-C Goal (mg/dL) Non-HDL-CGoal (mg/dL) CHD and CHD Risk Equivalent (10-year risk for CHD >20% <100 <130 Multiple (2+) Risk Factors and 10-year risk <20% <130 <160 0–1 Risk Factor <160 <190

  26. Specific Dyslipidemias: Causes of Low HDL Cholesterol (<40 mg/dL) • Elevated triglycerides • Overweight and obesity • Physical inactivity • Type 2 diabetes • Cigarette smoking • Very high carbohydrate intakes (>60% energy) • Certain drugs (beta-blockers, anabolic steroids, progestational agents)

  27. TC: 200 mg/dL HDL: 25 mg/dL LDL: 160 mg/dL TG: 75 mg/dL TC: 200 mg/dL HDL: 70 mg/dL LDL: 100 mg/dL TG: 150 mg/dL Risk Can Vary Considerably with Same TC

  28. TC: 200 mg/dL HDL: 25 mg/dL LDL: 160 mg/dL TG: 75 mg/dL This person would be at high risk for CHD based on lipid profile TC: 200 mg/dL HDL: 70 mg/dL LDL: 100 mg/dL TG: 150 mg/dL This person would be at low risk for CHD based on lipid profile Risk Can Vary Considerably with Same TC

  29. Risk Can Vary Considerably with Same TC • TC: 200 mg/dL • LDL-C: 120 mg/dL • HDL-C: 30 mg/dL • TG: 450 mg/dL • 42 y.o. man, smoker • What is his LDL goal?

  30. Risk Can Vary Considerably with Same TC • TC: 200 mg/dL • LDL-C: 120 mg/dL • HDL-C: 30 mg/dL • TG: 450 mg/dL • 42 y.o. man, smoker • What is his LDL goal? • A: he has 3 risk factors (male, smoker, low HDL), non-CAD, so his LDL goal is 130 mg/dL

  31. Risk Can Vary Considerably with Same TC • TC: 200 mg/dL • LDL-C: 120 mg/dL • HDL-C: 30 mg/dL • TG: 450 mg/dL • If TG are >200 mg/dL, determine non-HDL cholesterol • TC – HDL = 170 mg/dL • What is his goal?

  32. Risk Can Vary Considerably with Same TC • TC: 200 mg/dL • LDL-C: 120 mg/dL • HDL-C: 30 mg/dL • TG: 450 mg/dL • Non-HDL-C goal is LDL goal + 30 • Patient has 2+ risk factors so goal is <130 mg/dL • Non-HDL goal is 160 mg/dL

  33. Blood Urea Nitrogen • Normal value: 10-20 mg/dl • High: prerenal causes (CHF), renal obstruction, excessive intake of protein, GI bleeding, catabolic state, dehydration, glucocorticoid therapy; not specific to renal disease, though most renal diseases cause  BUN • Low: inadequate dietary protein, severe liver failure

  34. Creatinine • Normal value: 0.7-1.2 mg/dL • Breakdown product of creatine, an important component of muscle • Production depends on muscle mass, which varies very little. • Excreted exclusively by the kidneys • Level in the blood is proportional to the glomerular filtration rate. • A more sensitive test of kidney function than BUN because kidney impairment is almost the only cause of elevated creatinine.

  35. Creatinine • Rising creatinine may indicate impending renal failure • Abnormal values appear late in chronic renal failure • Baseline creatinine will be low if patient muscle mass is low • Rise of 0.3 to 0.5 mg/dL/day is a clinically significant rise

  36. BUN to Creatinine Ratio • Normal range 10-20:1 • In kidney disease, the BUN:creatinine ratio is usually normal • Increased BUN to creatinine ratio is commonly caused by intravascular depletion (sodium, water and urea are retained by the body; creatinine is excreted)

  37. BUN to Creatinine Ratio • High BUN:creatinine ratio may also be caused by protein loads in PN or EN; usually does not exceed 30 mg/dL • Can also be caused by renal obstruction (e.g. kidney stones), poor renal perfusion or acute renal failure; medications including diuretics, corticosteroids, • Very high levels may be caused by GI or respiratory bleeding

  38. Dehydration • Excessive loss of free water • Loss of fluids causes an increase in the concentration of solutes in the blood (increased osmolality) • Water shifts out of the cells into the blood • Causes: prolonged fever, watery diarrhea, failure to respond to thirst, highly concentrated feedings, including TF

  39. Input < output over time Decreased weight Sunken, dry eyes Dark-colored urine; oliguria Dry mucous membranes Sticky saliva Poor skin turgor Cool, pale, clammy skin Assessment of Hydration StatusPhysical Signs of Underhydration

  40. Elevated sodium Elevated chloride Elevated BUN Elevated creatinine Elevated hemoglobin Elevated hematocrit Elevated serum osmolality Elevated urine specific gravity Assessment of Hydration StatusLaboratory Signs of Underhydration

  41. Laboratory Values and Hydration Status Adapted from Charney and Malone. ADA Pocket Guide to Nutrition Assessment, 2004.

  42. Laboratory Values and Hydration Status Adapted from Charney and Malone. ADA Pocket Guide to Nutrition Assessment, 2004.

  43. Laboratory Values and Hydration Status Adapted from Charney and Malone. ADA Pocket Guide to Nutrition Assessment, 2004.

  44. Laboratory Values and Hydration Status Adapted from Charney and Malone. ADA Pocket Guide to Nutrition Assessment, 2004.

  45. Laboratory Values and Hydration Status Adapted from Charney and Malone. ADA Pocket Guide to Nutrition Assessment, 2004.

  46. Laboratory Values and Hydration Status Adapted from Charney and Malone. ADA Pocket Guide to Nutrition Assessment, 2004.

  47. Treatment of Dehydration • Use hypotonic IV solutions such as D5W • Offer oral fluids • Rehydrate gradually

  48. Check potassium, phosphorus, magnesium prior to initiation of feeding in high-risk individuals A rapid decline along with fluid retention, derangements of glucose metabolism is seen with refeeding Correct low levels prior to initiation of hypocaloric feeds (<BEE x 1) and monitor daily until stable at full feeds At risk pts are those with anorexia nervosa, alcoholism, prolonged IV hydration or fasting Lab Data in Refeeding Syndrome

  49. Stool Studies: C. Difficile • C. difficile associated diarrhea, cramps, fever, leukocytosis usually occurs within 1-2 mos of antibiotic use • Cytotoxin B is the most specific assay (toxin in stool); may need to test several times • Treatment: metronidazole or oral vancomycin • Avoid antidiarrheals

  50. Stool Studies: Fat Malabsorption • Sudan III stain: qualitative study, can use random stool sample; positive results are increased (2+) or markedly increased (3+); more reliable for moderate to severe steatorrhea • Fecal fat test: pt consumes 80-100 g fat/day a 72-H stool collection is made; <7 g fat/24-h stool collection is normal

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