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Ch18 LABORATORY DATA IN NUTRITION ASSESSMENT

Ch18 LABORATORY DATA IN NUTRITION ASSESSMENT. I.  Definition and Usefulness of Nutrition Laboratory Data

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Ch18 LABORATORY DATA IN NUTRITION ASSESSMENT

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  1. Ch18 LABORATORY DATA IN NUTRITION ASSESSMENT I.  Definition and Usefulness of Nutrition Laboratory Data *Nutrition-specific laboratory data: information about nutrition status obtained from controlled physical, chemical, molecular diagnostic or microscopic examination of specimens of body tissues, fluids, and wastes.

  2. II. Specimen Types • 1. Serum • 2. Plasma • 3. Erythrocytes (RBC) • 4. Leukocytes (WBC) • 5. Other tissues (scrapings or biopsy) • 6. Urine • 7. Feces • 8. Less commonly used: Saliva, Hair, Nails, Sweat, Blood spots

  3. III.Types of Assays 1.Static assay: measures the actual level of nutrient in the specimen, Ex. Serum Fe, WBC ascorbic acid, hair Zn etc. 2.Functional assay: quantitatively measures the magnitude of a biochemical activity that is dependent on the nutrient of interest. Ex. Blood ferritin (iron storage) - not always specific

  4. IV. Assessment of Protein-Energy Status A. Hormonal and Cell-Mediated Response to Stress * Negative acute phase respondents: Alb., Tf, prealb., RBP↓ *Positive acute phase respondents: C-reactive protein, serum amyloid A, fibrinogen (Box 18-1), haptoglobin, alpha1-acidglycoprotein, alpha1-antitrypsin, alpha1-antichymotrypsin, ceruloplasmin, C3 & C4

  5. B. N Balance N balance = N intake – N output N intake = prot. (g) intake/6.25 N output = UN + obligatory N loss (2g) N balance = N intake – (UN+2 g) or (UUN+4 g) △ very accurate record of intake & output a. A healthy person → 0 balance b. Starvation & severe PEM →Θ balance c. Preg., growing kids, recovery pt.→ ⊕balance

  6. C. Visceral (Plasma) protein Indicators - plasma and extra-vascular fluids proteins represent 3% of total body protein, visceral organ protein ～ 10% - functional indices of hepatic protein status or visceral protein balance, ∵syn. In the liver. - integrate protein syn. and degradation over longer periods. ( N balance assesses only short-term changes.)

  7. Table 18-1 Properties of proteins commonly used in protein-energy assessments • Albumin (Alb) • Transferrin (Tf) • Transthyretin (TTHY): prealbumin • Retinol-Binding Protein (RBP)

  8. Albumin • The most intensively studied of all proteins • Alb. Probably only reflects protein intake in specialized experimental conditions • Alb. ↓dramatically in protein-free diets, but are more preserved in total starvation • Alb. Is a negative acute-phase reactant and it has long half-life (～20 days) • Large extra-vascular alb. Pool (1.5 – 2.0X), return to the blood, • Poor index of PEM

  9. 2. Transferrin - negative acute-phase respondent - half-life 8 days - responsive to dietary protein and energy, controlled by the size of the Fe storage pool. Fe depleted →↑Tf synthesis. - slightly more useful than Alb. As a marker of PEM

  10. 3. Transthyretin (prealbumin, TTHY) • - Binds retinol-binding protein & Thyroxin • - Correlate with short-term changes in PEM status • - A negative acute-phase protein, ↓level ∵inadequate nutrition or inflammatory stress. • - half-life: 2 days, very useful in monitoring improvements in PE status • - Zn def. affects hepatic TTHY synth. and secretion

  11. 4. Retinol-Binding Protein • - half-life: 12 hrs. • - circulate in a complex with TTHY • - Retinol-RBP-TTHY complex→ peripheral tissue → release retinol →RBP-TTHY dissociated → apo-RBP filtrated by glomerulus • - Plasma RBP correlated with PE status in uncomplicated PEM • - Negative acute-phase prot., does not reflect PE status in acutely stressed pt. • -Vitamin A status & renal function influ. RBP

  12. 5. C-Reactive Protein (CRP) • Positive acute-phase respondent protein • - ↑early in acute stress (within 4 – 6 hrs), as much as 1000X • - CRP↓→anabolic period of inflammatory response, ∴more intensive nutr. therapy is beneficial

  13. D. Somatic Indicators of PEM • Urinary Creatinine and Creatinine-Height Ratio (CHI) - Creatine → Creatinine (exclusively in muscle tissue) → excreted • Creatinine: ♂>♀ , Greater muscle>smaller muscle

  14. Muscle (kg) = k + k’ (urinary creatinine) • K & k’ are empirical constants • Skeletal Muscle Mass (kg) = 4.1+18.9 x 24-h creatinine excret. g/d

  15. CHI = 24-h urine vol. (dl) X U. creatinine conc (mg/dl). Expected 24-h urine creatinine excretion (mg) • Used with caution in tall, thin, or muscular individual • Individual variability in daily creatinine excretion • Quantitative urine collections (24-h)?

  16. 2. 3-methylhistidine Excretion • 3-methylhistidine found only in the actin and myosin of muscle tissue • Is released and cannot be recycled • Ass. With muscle mass • Requires labor-intensive assay procedures • Is difficult to estimate accurately

  17. LABORATORY DATA IN NUTRITIONAL ANEMIA • Anemia: • 1. ↓# of R.B.C./blood vol • 2. ↓Hb conc. *Definition: Hb. Conc. < 95%tile for healthy reference populations. *Anemia is not a disease, but a symptom of a variety of situations.

  18. A. Classification of Anemia • 1. Nutritional deficits • Mean red blood cell volume - Microcytic anemia: < 80 fL(10-15 L), Fe-def. - Normorcytic: 80 – 99 fL - Macrocytic anemia > 100 fL, folate-def. or B12 def.

  19. 2. Non-nutritional causes of anemia - Leukocyte & platelet counts: ↓: marrow failure ↑: leukemia, infection - Normal size RBC: acute blood loss

  20. B. Laboratory Tests for Iron Deficiency Anemia • Serum Fe * A relatively poor indicator of Fe status , ∵large day-to-day changes, also a diurnal variation (the highest in the mid-morning and lowest at the mid-afternoon)

  21. 2. TIBC (total iron binding capacity) & Transferrin saturation * 2 ferric ions & 2 bicarbonate ions / Tf * Fe-depletion: Tf↑, Tf saturation↓, TIBC ↑(# of free binding sites on plasma Tf) * Exceptions: Tf↑during hepatitis, hypoxia, preg. OC or estrogen replacement.

  22. TIBC↓: malignant dz, nephritis, acute and chronic inflammatory dz, megaloblastic anemias, hemolytic anemias, PEM, fluid overload, liver dz. *Tf saturation is useful in screening for hemochromatosis (values>60%)

  23. 3. Zinc Protoporphyrin: Heme Ratio (ZPPH) and Free-Erythrocyte Protoporphyrin Protoporphyrin IX + Fe → heme Protoporphyrin + Zn → ZPP Fe-repletion: ZPPH 1/20,000 • Fe-depletion: ZPPH 1/12,000 • ZPPH is unaffected by hydration status or recent blood loss

  24. 4. Ferritin • Serum ferritin: a indicator of Fe storage • Serum ferritin conc. is directly proportional to the amount of ferritin inside storage cells (liver, spleen, and marrow)

  25. C. Effect of Inflammation on Anemia • *Serum ferritin↑ during inflammation ∵cytokines and other inflammatory mediators ↑ferritin syn. or ferritin leakage *anemia of chronic disease(ACD): inflammatory, infectious, and neoplastic disorders • Inflammation→ ↓RBC production • Anti-inflammatory drugs→ GI bleeding • Inflammatory blockage of Fe transport

  26. *Serum Transferrin Receptor (sTfR) - Binds to holotransferrin (Tf-Fe(III)) - Test for Fe Deficiency: not affected by inflammatory status *↑sTfR correlated to Fe def.

  27. D. Laboratory Assessment of Macrocytic Anemias Associated with B Vitamin Def. 1. Static test for Folate and Vitamin B12 status a. Whole blood folate – serum folate = RBC folate (1) microbes’ growth (2) radio-binding assays (3) immunoassays

  28. b. Serum folate (fasting) is as good as RBC folate c. Serum B12

  29. 2. Functional Tests to Determine the Causes of Macrocytic Anemias a. Homocysteine Methionine + Methyl group + Adenine ↓ SAM (S-adenosylmethionine) ↓ ↘ S-adenosyl homocysteine CH3 ↓ Homocysteine B12, Folate ↓ ↓B6 Methionine Cysteine *Folate & vit. B12 def. →↑ homocysteine

  30. b. Methylmalonic Acid *Degradation from valine or odd-number fatty acids Vit. B12 def. B12 Methylmalonyl CoA → Succinyl CoA ↘ Methylmalonic Acid↑(serum & Urine)

  31. c. Vitamin B12 Malabsorption * Schilling test (1) Oral radio-labeled vit. B12 + injection Vit. B12, detect urinary radio-labeled vit. B12 (2) Oral radio-labeled vit. B12 + intrinsic factor, detect urinary radio-labeled vit. B12

  32. Laboratory Markers of Mal-absorption Chapter 30 Mal-absorption syndromes: ↓absorption fat and fat-soluble substances

  33. Wellness Assessment • Lipid Indices of Cardiovascular Risk - Total Chol. • LDL-Chol. • HDL-Chol. • TG

  34. Box 18-2 New lipid and lipoprotein CVD risk factors • Small (more dense) LDL particles • ↑apo-protein B conc. • ↓apo-protein A-I conc. • ↑remnant lipoprotein chol. & TG conc.

  35. b. Indices of Oxidative Stress *ROS: Fig. 18-2 (1) Antioxidant Status - antioxidant vitamins (E & C) - minerals (Se) - dietary phytochemicals (carotenoids, lycopene ect.) - endogenous antioxidant compounds and enzymes (SOD and glutathione) - New directions (p.448) Biophotonic measurement of antioxidant capacity

  36. (2) Markers of Oxidative Stress Table 18 - 3 Markers of Oxidative Stress (3) Homocysteine Table 18 - 4 CVD risk and plasma homocysteine concentration Box 18 – 3 Homocysteine and CVD

  37. c. Clinical Chemistry Panels Table 18-5 Constituents of the common serum chemistry panels

  38. d. The Complete Blood Count Table 18-6 constituents of the hemogram; complete blood count and differential

  39. e. Urinalysis 1. The urine’s appearance 2. The results of basic tests done with chemically impregnated reagent strips • The microscopic exam. of urine sediment Table 18-7 Chemical tests in a urinalysis

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