In: Nursing
A 54-year-old male presents to the clinic with severe pain in his left wrist and right great toe. The affected joints are swollen, erythematous and painful. The patient has limited range of motion of these joints. He denies injury to these areas. The patient is afebrile with a temperature of 98.8, all vital signs are within normal limits.
The patient has a history of hypertension and hyperlipidemia. He has been steadily gaining weight over the past few years and is now about 50 pounds overweight. He states that he drinks four to five beers each night and loves his steaks!
Serum Lab values:
WBC 5,400 Glucose 85 mg/dL Uric Acid 10.7 mg/dL BUN 8 mg/dL Creatinine 0.9 mg/dL Synovial fluid analysis showed many intracellular needle?shaped crystals; negative birefringence
1. Which of the lab values is the most likely cause of this patient’s swelling in his wrist and toe? Explain why this can cause pain.
2. Describe the metabolic steps that produce the compound that is responsible for the pain in his joints.
3. What is the most likely diagnosis?
4. What is the most likely mechanism causing the abnormal lab value in this case?
5. Describe the coupled enzymatic method for measurement of the elevated lab value. List any interfering substances.
1. Which of the lab values is the most likely cause of this patient’s swelling in his wrist and toe? Explain why this can cause pain.
The patient’s uric acid value is 10.7 mg/ dL, and the normal uric acid value for male rages from 3.4-7.0 mg/dL. The excess uric acid in the bloodstream can be deposited in the joints as crystals lead to inflammation and can cause pain, heat. Redness, swelling(cardinal signs of inflammation). Gout more commonly occurs in people regularly eat meat or seafood, drink beer, or are overweight.
2. Describe the metabolic steps that produce the compound that is responsible for the pain in his joints.
Abnormal purine metabolism can cause gout. The final product of purine metabolism will be uric acid, The excess of uric acid crystallizes in the form of monosodium urate, which will form tophi or crystals on tendons and surrounding tissue of the joints. Microscopic may not cause inflammation as it may be walled off by a ring of proteins and this will block the interaction of the crystals with cells and avoids inflammation. The naked crystals may detach from the wall as a result of minor physical damage to the joint, medical or surgical stress, or rapid changes in uric acid levels. That can trigger a local immune-mediated inflammatory reaction in macrophages and result in inflammation. This is initiated by the NLRP3 inflammasome protein complex. The loss of urate oxidase (uricase) the enzyme which breaks down uric acid, in humans and higher primates have made this condition common.
3. What is the most likely diagnosis?
Gout or Gouty arthritis
4. What is the most likely mechanism causing the abnormal lab value in this case?
Hyperuricemia can cause gout and can be resulted from either excess uric acid production or reduced excretion or a combination of both mechanisms. Any mechanism that alters uric acid homeostasis like inborn metabolic errors (biochemically and genetically heterogeneous disorder).
5. Describe the coupled enzymatic method for measurement of the elevated lab value. List any interfering substances.
The coupled enzymatic method is based on the oxidative coupling reaction between the N-methyl-N-(4-aminophenyl)-3-methoxyaniline (NCP) reagent and the hydrogen – donor reagent, N-ethyl-N-(2-hydroxy-3-sulfopropyl)-3-methylaniline (TOOS). The system involves three enzymes: uricase, peroxidase and ascorbate oxidase. Uric acid concentrations up to 1.428 mmol/L, with a relative standard deviation of up to 1.8 % can be identified by this method. In this method, the effect of the medium pH and the NCP concentration on the linearity of the chromogen absorbance against the uric acid concentration curve was investigated along with the influence of the uricase activity on the maximum rate of uric acid oxidation. The effective use of the NCP reagent will result in a more accurate and more sensitive determination of the uric acid compared to the determination with 4-aminoantipyrine
(4-AA) as the coupling regent.
Substances interfere with this uric acid determination.
Ascorbic Acid: No significant interference up to 20 mg/dL Ascorbate
Bilirubin: No significant interference up to 40 mg/dL Bilirubin
Hemolysis: No significant interference up to 500 mg/dL Hemolysate
Lipemia: No significant interference up to 1000 mg/dL Intralipid*