MLS 301 - Clinical Chemistry 1 Past Lectures PDF

MLS 301 – CLINICAL CHEMISTRY 1 First Semester AY 2024-2025 Zharina Leih Panopio-Atienza | Loren Deduyo Instructors College of Allied Medical Professions  COPYRIGHT NOTICE This materia...

MLS 301 – CLINICAL CHEMISTRY 1 First Semester AY 2024-2025 Zharina Leih Panopio-Atienza | Loren Deduyo Instructors College of Allied Medical Professions  COPYRIGHT NOTICE This material has been reproduced and communicated to you or on behalf of Lyceum of the Philippines University- Batangas pursuant to PART IV: The Law of Copyright of Republic Act RA 8293 or the "Intellectual Property Code of the Philippines". The University does not authorize you to reproduce or communicate this material. The material may contain works that are subject to copyright protection under RA 8293. Any reproduction, and/or communication of the material by you may be subject to take legal action against such infringement. Do not remove this notice. This material is prepared by the Faculty of the Department of Medical Laboratory Science, LPU-Batangas College of Allied Medical Professions, solely for the use of students enrolled in MLS 301- Clinical Chemistry 1 for the A.Y. 2024- 2025. Please do not distribute without permission. NON-PROTEIN NITROGENOUS (NPN) SUBSTANCES (Kidney Function Tests) College of Allied Medical Professions Medical Laboratory Science  OBJECTIVES List the nonprotein nitrogen components of the blood and recognize their chemical structures and relative physiologic concentrations. Describe the biosynthesis and excretion of urea, uric acid, creatinine, creatine, and ammonia. Describe the major pathological conditions associated with increased and decreased plasma concentrations of urea, uric acid, creatinine, creatine, and ammonia. Suggest possible clinical conditions associated with test results, given patient values for urea, uric acid, creatinine, and ammonia and supporting clinical history.  OUTLINE I. Urea II. Creatine and Creatinine III. Uric Acid IV. Ammonia  NON PROTEIN NITROGEN § Substances in the blood which contain nitrogen but are not considered as proteins § End products of the metabolism of nucleic acids, amino acids and proteins § The determination of NPNs in the blood (specifically UREA and CREATININE) has traditionally been used to monitor renal function and thus test for NPNs is part of KIDNEY FUNCTION TEST (KFT) KIDNEY Paired, bean-shaped organ located retroperitoneally Each kidney is comprised of 1-1.5 million nephrons - the functional unit of the kidney Receives approximately 20-25% of the total cardiac output Functions: 1.Elimination of waste products 2.Maintenance of Blood Volume 3.Maintenance of electrolyte balance 4.Maintenance of acid-base balance 5.Secretion of erythropoietin 6.Activation of Vitamin D  UREA § Major excretory product of PROTEIN metabolism. It has the molecular weight of 60 Daltons. § Urea is 90% excreted and 10% reabsorbed § PCT: Passive (reabsorption is NOT mediated by urea transporters) § Collecting ducts: Active (reabsorption is mediated by urea transporters) § Depends on urine flow rate and extent of hydration § Synthesized solely in the liver from ammonia, CO2 and H2O through the urea or Krebs-Henseleit cycle. 2 NH3 + CO2 + 3 ATP + H2O → urea + 2 ADP + 4 Pi + AMP  UREA § Urea is a toxic by product which is normally removed from the blood by the kidneys. § If the kidneys are impaired, urea is not removed in the blood and accumulates in the blood. § The concentration of urea in the plasma is determined by the § protein content of the diet § the rate of protein catabolism § renal function and perfusion § An increase in the concentration of serum or plasma urea may indicate a defect in the filtering system of the kidneys. § Measured by its nitrogen content (Urea = BUN x 2.14)  UREA § First to increase in a renal/kidney disease although it requires 70-80% glomerular damage before the concentration of urea is increased in the blood. § Screening procedure for kidney function § Easily removed by dialysis § Urea results are effective for diagnosis if combined with creatinine results CLINICAL APPLICATION Measurement of urea is used to: 1. Evaluate renal function 2. Assess hydration status 3. Determine nitrogen balance 4. Aid in the diagnosis of renal disease 5. Verify adequacy of dialysis DISEASE CORRELATIONS § Azotemia- elevated concentration of NPNs in the blood. § Classified into pre-renal, renal or post-renal depending on the etiology 1. Pre-renal azotemia - caused by § Reduced renal blood flow § congestive heart failure § Increased protein catabolism § stress § shock § fever § hemorrhage § major illnesses § dehydration § corticosteroid therapy § High protein diet § GI hemorrhage DISEASE CORRELATIONS 2. Renal azotemia- caused by 3.Post-renal azotemia- caused damage within the kidneys by obstruction of urine flow such as § acute and chronic renal anywhere in the urinary tract by failure §renal calculi § glomerulonephritis §tumors of the bladder or § tubular necrosis prostate § other intrinsic renal §severe infection disease DISEASE CORRELATIONS § Urea levels in the blood are decreased in the following conditions: 1. Poor nutrition 2. High fluid intake / excessive intravenous (IV) fluids 3. Pregnancy 4. Severe liver diseases 5. Effects of some hormones 6. Severe vomiting and diarrhea DISEASE CORRELATIONS § Uremia § Very high plasma urea concentration accompanied by renal failure § The kidneys fail to eliminate waste products of metabolism. § Clinical findings: § Normocytic normochromic anemia § Uremic frost (dirty skin) § Generalized edema § Foul-breath § Urine-like sweat § Presence of BURR cells in the PBS UREA: CREA RATIO § Normal Urea N: Crea Ratio § Post-renal azotemia § 10:1 to 20:1 § Increased plasma urea § Pre-renal azotemia § Increased plasma crea § Increased plasma urea § Increased Urea N: Crea Ratio § Normal plasma crea § Decreased Urea N:Crea § Increased Urea N: Crea Ratio Ratio § Decreased urea production  CREATINE AND CREATININE § Creatinine is derived from creatine and creatine phosphate in a nonenzymatic process in the muscles § Creatine is synthesized primarily in the liver from arginine, glycine, and methionine § Creatine is transported to muscle tissues where it is converted to creatine phosphate. § Plasma creatinine concentration is a function of § Muscle mass § Rate of creatine turnover § Renal function § Creatine phosphate loses phosphoric acid and creatine loses water to form the cyclic compound, CREATININE, which diffuses into the plasma and is excreted in the urine.  CREATININE § Major end product of MUSCLE metabolism § An additional source of creatinine is creatine contained in ingested meat or dietary supplements. Conversion of creatinine from creatine in meat is enhanced by high temperature and low pH § Not reused by the body; solely a waste product (100% excreted; maximum of 1% reabsorbed) § NOT easily removed by dialysis § Can be used to check for the completion of a 24-hour urine  CREATININE § Plasma creatine concentration is a function of: § Relative muscle mass § Rate of creatine turnover § Renal function § Creatinine is also used to evaluate fetal maturity, as gestation progresses, more creatinine is excreted by the fetus into the amniotic fluid (2mg/dL) § Plasma creatinine is a relatively insensitive marker and may not be measurably increased until renal function has deteriorated more than 50%. CLINICAL APPLICATION 1. Determine the sufficiency of kidney function Elevated creatinine concentration is associated with abnormal renal function Plasma concentration of creatinine is inversely proportional to the clearance of creatinine 2. Monitor the progression of kidney disease  URIC ACID § Major end product of PURINE (adenine, guanine) NUCLEIC ACID metabolism § Formed from xanthine by the action of xanthine oxidase in the liver and intestine. § More than 95% of uric acid in the body fluids exist as monosodium urate § Plasma pH of 7= urate insoluble § >6.8mg/dL conc.= urate crystals may form and precipitate in tissues § Most are reabsorbed in the proximal tubules § In other mammals, the enzyme uricase further oxidizes uric acid to allantoin  URIC ACID § The loss of uricase in higher primates parallels the similar loss of the ability to synthesize ascorbic acid. § Both uric acid and ascorbic acid are strong reducing agents (electron donors) and potent antioxidants. In humans, over half the antioxidant capacity of blood plasma comes from uric acid. § Uric acid is relatively insoluble in plasma and, at high concentrations, can be deposited in the joints (tophi) and tissue, causing painful inflammation § In acidic urine (pH 7 mg/dL). This is associated with: § Increased uric acid production § Decreased renal excretion CLINICAL APPLICATION Causes of hyperuricemia 1.Gout § Degenerative disorder; commonly found in men between 30 and 50 years of age and women after menopause § Affected individuals have pain and inflammation of the joints caused by precipitation of sodium urates § In 25% to 30% of these patients, hyperuricemia (>6.0 mg/dL) is a result of overproduction of uric acid § Patients are susceptible to the formation of renal Picture source: https://universityhealthnews.com/daily/bones- calculi joints/gout-in-foot/ CLINICAL APPLICATION Causes of hyperuricemia 2. Increased catabolism of nucleic acids Chemotherapy for proliferative diseases such as leukemia, lymphoma, multiple myeloma, and polycythemia Treatment: Allopurinol - inhibits xanthine oxidase (EC 1.1.3.22), an enzyme involved in uric acid synthesis 3. Renal disease 4. Hemolytic or megaloblastic anemia CLINICAL APPLICATION Causes of hyperuricemia 5. Ingestion of diet rich in purines (liver, kidney, sweetbreads, and shellfish) or various disease processes. 6. Starvation due to increased tissue catabolism 7. Decreased uric acid excretion Glycogen storage diseases Fructose intolerance Toxemia of pregnancy Lactic acidosis Due to excess production of metabolites (TAG and lactate) which competes with urates for renal excretion CLINICAL APPLICATION Causes of hyperuricemia 8. Inherited disorders of purine metabolism Lesch-Nyhan syndrome An X-linked genetic disorder (seen only in males) caused by the complete deficiency of hypoxanthine-guanine phosphoribosyltransferase (EC 2.4.2.8), an important enzyme in the biosynthesis of purines. Lack of this enzyme prevents the reutilization of purine bases in the nucleotide salvage pathway and results in increased de novo synthesis of purine nucleotides and high plasma and urine concentrations of uric acid. CLINICAL APPLICATION 2. Hypouricemia Less common than hyperuricemia Causes: Severe liver diseases Defective tubular reabsorption (Fanconi syndrome) Chemotherapy with 6-mercaptopurine or azathioprine (inhibitors of de novo puine synthesis) Overtreatment with allopurinol  AMMONIA § Ammonia (NH3) is produced from the catabolism of amino acids and by bacterial metabolism in the lumen of the intestine § Liver is the sole site of ammonia detoxification via the urea cycle § Loss of hepatocytic function occurs, serum ammonia levels are elevated § At normal physiologic pH, most ammonia in the blood exists as ammonium ion (NH4+). § Ammonia is excreted as ammonium ion by the kidney and acts to buffer urine  AMMONIA Free ammonia is neurotoxic and often associated with encephalopathy. Toxicity may be partly a result of increased extracellular glutamate concentration and subsequent depletion of adenosine triphosphate in the brain Increased blood ammonia is seen in Hepatic failure (test for ammonia is a part of the LIVER FUNCTION TESTS) Reye's syndrome Inherited deficiencies of urea cycle enzymes Although classified as an NPN, it is NOT a good indicator of kidney function.  AMMONIA Reye's syndrome A serious, fatal disease common in children frequently preceded by a viral infection and the administration of aspirin An acute metabolic disorder of the liver and brain in which there is fatty infiltration of the organs. Thank you for listening