Nutrition Assessment: Role of Laboratory Data Liz Hudson MPH, RD September, 21st 2016 Laboratory Assessment and Nutrition Care Process • Objective measure: diagnose diseases, support nutrition diagnoses, monitor medication effectiveness, and evaluate NCP interventions – Many things are involved with interpretation • Age • Pt condition • Medical condition • Hydration Status • Fasting status • Interpretation with regard to nutrition can be tricky, but is essential for the nutrition expert Biomarkers: Next big thing or buzzword? • “Precision medicine: (PM) is a medical model that proposes the customization of healthcare, with medical decisions, practices, and/or products being tailored to the individual patient.” wikipediahttps://en.wikipedia.org/wiki/Precision_medicine • Biomarkers: often not that easy to interpret – Not necessarily a better measure of what you are doing than just asking the person Definition of Specimen Types • Whole blood: Used when entire content of blood is to be evaluated – no elements are removed • Serum: The fluid obtained from blood after the blood has been clotted and then centrifuged to remove the clot and blood cells • Plasma: liquid component of blood (water, blood proteins, inorganic electrolytes, clotting factors) • Erythrocytes: red blood cells • Leukocytes: white blood cells • Other tissues: scrapings and biopsy samples • Urine: random samples or timed collections • Feces: random samples or timed collections • Less common: saliva, nails, hair, sweat, breath tests Interpretation of Routine Medical Laboratory Tests • Clinical chemistry panels – Basic Metabolic Panel – Comprehensive Metabolic Panel • Complete Blood Count • Urinanalysis • Hydration Status • Serum Proteins • Vitamin D Clinical Chemistry Panels • Basic Metabolic Panel • Comprehensive Metabolic Panel – Glucose – Glucose – Calcium – Calcium – Sodium – Sodium – Potassium – Potassium – CO2 (bicarbonate) – CO2 (bicarbonate) – Chloride – Chloride – BUN (blood urea nitrogen) – BUN (blood urea nitrogen) – Creatinine – Creatinine – Albumin – Total Protein – ALP – ALT – AST – Bilirubin Examples Considerations regarding interpretation: Electrolytes • Sodium (Na): 136 to 144 mEq/L – Hyponatremia: most common electrolyte abnormality in hospitalized patients • Usually caused by excessive hypotonic IV fluid intake and/or gastrointestinal losses of sodium-rich fluids (gastric suctioning, diarrhea, high ileostomy output) • High serum glucose concentrations increase plasma osmolality to cause fluid shift from intracellular space to plasma – resulting in hyponatremia – Hypernatremia: commonly the result of impaired water intake or relative water deficit Considerations regarding interpretation: Electrolytes • Potassium: 3.5-5 mEq/L (minimally affected by diet) • Hypokalemia: decreases can be seen in excessive GI losses (diarrhea), intracellular shift during refeeding, medications (loop and thiazide diuretics increase K+ losses) • Hyperkalemia: decreased kidney function, medications (potassium-sparing diuretics, cyclosporine, tacrolimus) Considerations regarding interpretation: Electrolytes • Acid base disorders are usually caused by the patient’s underlying diseases and clinical condition(s) • Chloride: 100-110 mEq/L – Hyperchloremic acidosis: may result from large and rapid infusion of normal saline fluids or significant bicarbonate losses from intestines or kidneys (can cause chloride retention) • Bicarbonate or total Co2: 21-30mEq/L – Metabolic alkalosis (increase in bicarbonate): prolonged vomiting, high gastric fluid suctioning, potassium wasting diuretic use Considerations regarding interpretation: Electrolytes • Blood Urea Nitrogen (BUN): 7-20mg/dL – Increased inkidney disease, dehydration, excessive protein catabolism – Decreased in liver failure, negative nitrogen balance, pregnancy (2nd or 3rd trimester) • Creatinine: 0.6-1.2 mg/dL – Increased in: poor kidney function – Decreased in: malnutrition Considerations regarding interpretation: Electrolytes • Calcium: 8.6-10 mg/dL. Serum levels related to many factors – Hypocalcemia: 45% of serum calcium is bound to serum albumin. A one gram decrease in serum albumin results in ~.8 mg decrease in serum calcium • Corrected calcium: measured serum calcium + 0.8 (4-serum albumin) • Ionized calcium (free calcium) is better measure of calcium status when albumin levels are low – Hypercalcemia: rarely caused by excess calcium intake • Common causes: malignancies, hyperparathyroidism, immobilization Corrected Calcium • Serum Calcium = 8.1 • Serum Albumin = 3.0 • Corrected Calcium = 8.1 + 0.8 (4.0-3.0) = 8.9 Considerations regarding interpretation: phosphorus (normal: 2.7-4.5mg/dL) • Serum phos a poor reflection of body stores because <1% is in ECF • Bones serve as a reservoir • Hypophosphatemia: <2.7 mg/dL • Impaired absorption (diarrhea, Vitamin D deficiency, impaired metabolism) • Medications: phosphate binding antacids, sucralfate, insulin, corticosteroids) • Alcoholism, especially during withdrawal • Intracellular shifts such as in refeeding syndrome • Increased losses: hyperparathyroidism, DKA recovery, hypomagnesemia Hyperphosphatemia • >4.5 mg/dL • Decreased renal excretion: acute or chronic renal failure; hypoparathyroidism – Sign of excessive dietary intake in patients on hemodialysis • Increased cellular release: tissue necrosis, tumor lysis syndrome • Increased exogenous phosphorus load or absorption, phosphorus containing laxatives or enemas, vitamin D excess Magnesium (normal: 1.3-2.5 mEq/L) • Magnesium homeostasis is maintained by the intestines, bone and the kidneys. • Hypermagnesemia: decreased kidney function can cause magnesium accumulation • Hypomagnesemia: common causes include diarrhea, high ileostomy fluid losses, medications (loop and thiazide diuretics, immunosuppressants) – Adequate correction of hypomagnesemia essential for correction of hypokalemia Clinical Chemistry Panels: Complete Blood Count (CBC) • Red blood cells • Hemoglobin concentration • Hematocrit • Mean cell volume (MCV) • Mean cell hemoglobin (MCH) • Mean cell hemoglobin concentration (MCHC) • White blood cell count (WBC) • Differential: indicates percentages of different kinds of WBC Example of CBC Laboratory Data to assess for nutritional anemias • Classification of Anemia need to distinguish • Iron deficiency anemia – Microcytic anemia: most often association with true iron deficiency • Important discriminating features are a low serum ferritin concentration, an increased total iron binding capacity (transferrin), and low serum iron concentration – Macrocyctic anemia: generally due to deficient utilization of folate or B12 by the blood cells • Pernicious anemia: not enough red blood cells due to lack of B12 • Megaloblastic anemia: folate deficiency • Anemia of chronic disease: (normocystic) does not respond to iron supplementation Tests for Iron Deficiency Anemias • Hemoglobin and hematocrit: below normal in all nutritional anemias. – Not sensitive for iron, vitamin B12, or folate deficiencies – Are sensitive to hydration status • Serum Ferritin: Primary intracellular Fe-storage, serum levels parallel iron stores – Increases during inflammatory response even when iron stores are not adequate – Not useful in anemia of chronic disease • Serum Iron: reflects recent iron intake, very insensitive index of total iron stores • Total Iron Binding Capacity (TIBC): – Increases when iron stores are depleted • Transferrin Saturation: decreased when iron stores depleted; low vitamin B6 and low transferrin saturation seen in aplastic anemia Tests for Macrocytic Anemias from B vitamin Deficiencies • Folate and B12 tests are not sensitive or specific to actual levels • Mean corpuscular volume or mean cell volume (MCV) is the average volume of red cells. – Decreased in iron deficiency – Increased in setting of vitamin B12 or folate deficiency Urinanalysis • Screening or diagnostic tool to detect substances or cellular material in the urine associated with different metabolic and kidney disorders • Often involves visual examination, dipstick test, and microscopic examination Urinanalysis • Acidity (pH): Abnormal pH levels may indicate a kidney or urinary tract disorder. • Concentration. A measure of concentration, or specific gravity, shows how concentrated particles are in your urine. Higher than normal concentration often is a result of not drinking enough fluids. • Protein: larger amounts may indicate a kidney problem. • Sugar: Any detection of sugar on this test usually calls for follow-up testing for diabetes. • Ketones: Positive in poorly controlled DM, fever, anorexia, starvation • Bilirubin: product of red blood cell breakdown. Bilirubin in urine may indicate liver damage or disease. • Evidence of infection: If either nitrites or leukocyte esterase — a product of white blood cells — is detected in your urine, it may be a sign of a urinary tract infection • Blood: it may be a sign of kidney damage, infection, kidney or bladder stones, kidney or bladder cancer, or blood disorders Types of Assays • Static assays: measures the actual level of the nutrient in the specimen (serum iron, white blood cell ascorbic acid) – Do not reflect the amount of that substance stored in the body – Highly influenced by recent dietary intake • Functional Assays: measure a biochemical or physiological activity that depends on the nutrient of interest (serum ferritin, TIBC) – Functional assays are not always specific to the nutrient (many biologic and physiologic functions involved) Assessment of Hydration Status: two main fluid compartments