9:30 – 11:00 essay questions
11:30 – 12:30 SAQ

                          

Module 3 0930 – 1045
Module 9 1120 – 1235
Module 7 1325 – 1440
Module 2 1500 – 1615

28th September EF10D

Module 8 0930 – 1045

                          

Date: Wednesday 27th July 2011

Start time: 9.30 am

Location: Humphreys Room, Medical School, U of B

Exam Board

Date: Wednesday 27th July 2011 (Following on from the Vivas above)

Start time: 4.00 pm

Location: Humphreys Room, Medical School, U of B

Morning and afternoon refreshments will be provided, with a buffet lunch at 12.00 noon.

Vivas will consist of a 10 minute talk followed by 10 minutes for questions.

                          

Room WF42 (was WF40A) located West Wing, First floor, Medical School, University of Birmingham

0930 – 1045     Module 5

1100 – 1330      Modules 4 & 6

1430 – 1545      Module 1

                          

Short Answer Questions. Answer all questions. Time allowed 1 hour.

There are 10 marks for each question

1)            Parathyroid hormone has a plasma half life of 3 minutes.  A patient undergoing a parathyroidectomy had an initial plasma value of 137 ng/L.  What was the level 11 minutes after isolation of the gland?  How long until the PTH level was undetectable? (Limit of detection = 5ng/L)

(5 marks each part)

2)              The following results were obtained on venous plasma glucose samples (mmol/L) during an oGTT

Fasting 2 hour Symptoms

Case 1 6.5 12.2 None

Case 2 6.6   7.8 None

Case 3 6.0   7.6 None

Case 4 6.9 15.0 Polyuria/Polydipsia

Case 5 6.1   7.7 None

Interpret the results in the light of the WHO criteria.

( 2 marks each)

3)            Define hypoglycaemia.  List 8 possible causes of hypoglycaemia in adults

(2 marks & 8 marks)

4)      Assuming the salt XCl₂ is completely dissociated in water and a 19g/L solution gave an osmolality of 600 mosmol/kg estimate the molecular weight of XCl₂

(10 marks)

5)      What volume of a stock glucose solution containing 9.01 g/L of glucose in saturated benzoic acid (5g/L) would be needed to make a litre of 8.33 mmol/L working standard?  What would be the concentration in g/L of benzoic acid in the final solution?

(6 marks & 4 marks)

6)     Write down the equation for Beer’s Law in terms of a) % transmission b) optical density.  State the units of any symbols used.

(6 marks & 4 marks)

7)      Calculate the hydrogen ion concentration in nmol/L of solutions of pH 6.9 and 7.6.

(5 marks each)

8)        Describe the current definitions for the metabolic syndrome

(10 marks)

9)  State the risk factors that are currently used to calculate cardiovascular disease risk.

(10 marks)

10)   Given the following patient results calculate the fractional excretion    of sodium:-

• • Serum:Urine
  • Sodium 146 mmol/L 50 mmol/L
  • Potassium    4.2 mmol/L
  • Chloride   94 mmol/L 57 mmol/L
  • Urea   34.4 mmol/L         100 mmol/L
  • Creatinine 450 umol/L   3.2 mmol/L
  • Osmolality 337 mmol/kg 325 mmol/kg

10 marks)

                          

Short Answer Questions.

Answer all questions.

Time allowed 1 hour.

A maximum of 10 marks will be awarded for each question

1. The transmittance of a solution of NADH at 340nm is 45%.  What is the absorbance of a 1 in 10 dilution of this solution?
2. List  the porphyrias that may present with acute attacks.
3. Name the enzyme that catalyses the rate limiting step of haem          synthesis and the product.
4. A radioisotope has a half life of 20 days.  What percentage of the initial activity is remaining after 10 days and 7 weeks?
5. A Family Doctor telephones for advice about results on a 24 year          old woman with anorexia nervosa. Serum results were:-

• • Sodium          141 mmol/L
  • Potassium     4.3 mmol/L
  • Urea       4.0 mmol/L
  • Creatinine          78 umol/L
  • Urate            37 umol/L  (149-446)
  • Bilirubin        2 umol/L
  • ALP                      73 IU/L (38-126)
  • ALT                 66 IU/L (<56)
  • Iron          6 umol/L
  • Transferrin      4.0 g/L
  • Transferrin saturation   6%
  • TSH                                      2.5 mU/L (0.5 – 4.2)
  • FT4          9.3 pmol/L  (10.8-19.3)
  • FT3          3.1 pmol/L  (3.5 -6.5)

What would you tell him?

1. A diabetic with a 24 hour creatinine clearance of 25mL/min and a serum creatinine of 180 umol/L was found to have an albumin excretion of 25 ug/min.  If the 24 hour urine has a volume of 2000 mL calculate the albumin/creatinine ratio in mg/mmol.
2. An endomysial antibody assay has been reported to have a diagnostic sensitivity of 88% and a diagnostic specificity of 97% for coeliac disease.  What is the probability that a positive result truly indicates coeliac disease in a group of subjects whose pre-test probability of coeliac disease is 1 in 1500?
3. List 5 ways in which Sickle cell disease may present clinically in       adults.
4. What is the pH of a 0.1 M aqueous solution of an acid of pKa = 4.756 in water at 25^oC?  State any assumptions you make.
5. A Family Doctor telephones you to ask advice about a 53 year old woman with hypertension, truncal obesity and abdominal striae.   What diagnosis is most likely and what first line test(s) would you suggest to investigate this potential diagnosis?
6. Calculate the approximate osmolality of an iv solution of dextrose saline containing 3% w/v glucose and 0.5% w/v sodium chloride

                          

Short Answer Questions. Answer all questions. Time allowed 1 hour.

1. A laboratory wishes to check that its equation for adjusting calcium for albumin is correct for its current methods.  A large dataset of paired calcium and albumin results is obtained from the laboratory computer, and a scatter plot of calcium (y-axis) versus albumin (x-axis) is graphed.  The linear correlation is confirmed with an equation (in the form of y = mx+c):

Calcium = 0.012 x Albumin + 1.776

a)   Using the equation and the desired reference range of 2.20 – 2.60 mmol/L, calculate the adjustment equation for this laboratory, expressed in the form:

Adjusted calcium = calcium + A (B – albumin)

What assumptions about the dataset do you need to make for the equation to be valid?

b)   The equation previously used by the laboratory was

Adjusted calcium = calcium + 0.025(40-albumin).

A patient had the results: Adjusted Ca 2.99 mmol/L, Albumin 22g/L.   What would the new adjusted calcium result now be for the same patient?

List the possible causes for the following results on a 45 year old woman in whom thyroid function tests were requested.  There were no clinical details on the request form.

Free T4 2 pmol/L  (10.0 – 24.0)

TSH 0.4 mU/L  (0.50 – 4.50)

1. Briefly describe 3 different analytical principles for estimating calcium and comment on the relative advantages /disadvantages.
2. A radioisotope has a half life of 12 days.  What percentage of the initial activity is remaining after 2 weeks and 7 weeks?
3. A 40 year old man complains of intermittent acute confusional episodes on awakening and after exercise which rapidly resolve with oral carbohydrate.  Four months previously he had a pituitary adenectomy for non-functioning benign pituitary adenoma.  Initial investigations reveal hypercalcaemia (serum corrected calcium = 2.70 mmol/L)  Further investigations are listed below

Synacthen test

Time (minutes) 0 30 60

Cortisol(nmol/L) 400 650 700

Prolactin, thyroxine, TSH, testosterone, LH, FSH, GH and IGF1 are all normal.

What is the likely diagnosis and list the further investigations?

The absorbance of a coloured solution is 1.2 in a 1cm cell at a concentration of 0.002M.  For a more accurate measurement an absorbance of 0.35 is required.  If the molecular weight of the coloured compound is 560, what weight of the compound should be used to prepare 10mL of the solution.

1. How would you prepare a 1 mol/l buffer pH 5.2 from sodium acetate and acetic acid (pka 4.74)
2. Calculate the approximate osmolality of an iv solution of dextrose saline containing 3% w/v glucose and 0.45% w/v sodium chloride.
3. Describe briefly the stepwise investigation of a patient suspected of having Cushings syndrome/disease.

10. A patient with severe water depletion has excreted only 100 mL of urine in the last 6 hours.  A short time before this the patient was found to have a creatinine clearance of 100 mL/min and a plasma creatinine of 100 umol/L.  Assuming the same clearance during the water depletion what would be the creatinine concentration in the latest 100 mL urine?

                          

West Midlands Training Course in Clinical Biochemistry & The University of Birmingham.

Short Answer Paper July 2004

Answer all questions.

Clinical Cases: -

• A 68 yr old woman on lithium, carbamezepine and lactulose has a 24 hour urine volume of 4.5litres. The results of a fluid deprivation test were: -

Time      Urine Vol    Urine Osm   Serum Na             Serum Osm

10.00h    150               180             149                 312

11.00h    200               177             150                 317

12.00h    150              175             151                 314

12.30                    2ugs Desmopressin given IM

13.00h      175             179             -                     311

14.00h      100             197             -                     303

15.00h      180             182             -                     297

16.00h      90              194             -                     301

Basal: Creatinine 138 umol/L                             (60 – 120)

Questions

• What abnormalities are apparent and what is the likely diagnosis?
• What is the most likely underlying cause in this particular case?
• What other endocrine abnormalities may sometimes be associated with the underlying cause?

• A 42 year old Caucasian man returns from a Mediterranean holiday and presents to the accident and emergency department giving a history of weakness, vomiting, and of dizziness on standing. The Casualty Officer  notices that the patient has a good sun tan but some unusual pigmentation also.

The following biochemistry was found: -

Sodium        118 mmol/L

Potassium    5.9 mmol/L

Urea             9.8 mmol/L

Creatinine    125 mmol/L

Questions: -

• Briefly highlight the abnormalities these results and suggest a possible endocrine cause for the presentation.
• What would be the most appropriate endocrine investigation to undertake at this time.
• Briefly describe  how the test should be performed and what precautions should be taken.

3.  A 60 year old woman complaining of lethargy and weight gain presented to her general practitioner. She has a family history of coronary artery heart disease and hypertension .

Total Cholesterol   10.0 mmol/L

HDL Cholesterol    1.8 mmol/L

Triglycerides          0.8 mmol/L

Creatinine Kinase   1534 IU/L                    (10-180)

Creatinine              145 umol/L                 (60 –120)

• The trainee GP contacts the laboratory for an interpretation of these data and suggestions for further immediate biochemical investigations. What would be your response?

4.  The following serum capillary zone electrophoresis (CZE) trace was obtained on  a sample  from 59 year old man complaining of  low back pain and fatigue. : -

Additional test results: -

Total Protein     77 g/L          (Ref Interval  60 – 85)

Albumin           42 g/L          (Ref Interval  35 – 48)

ESR                  26 mm/Hr     (Ref Interval 0 –14)

• Give a brief interpretation of the trace
• What is the most likely diagnosis?
• List further investigations that should be carried out on this sample.

• Using WHO criteria classify the following 75g oral glucose tolerance tests. Add any additional comments that you think should be appended to a report form. The values are for venous plasma glucose measurement: -

• A  55 year old lady complaining of polyuria and polydipsia

• A 55 year old  man attending a well man clinic  who had a fasting blood glucose of  6.2 other without symptoms.

c)  An obese 58 year old man with hypertension and a fasting  plasma glucose of  6.4 mmol/L.

d)  A 48 year old woman with weight loss, polyuria and polydipsia. Random plasma glucose  12.5 mmol/L and fasting plasma glucose 11.2 mmol/L.

• The following results were obtained on assay  of samples taken using a vacutainer system, from a 42 year old women attending a pre-operative assessment clinic.  The patient was due to undertake elective cosmetic surgery other wise well and not receiving any other medical treatment. The request form indicated that the patient had been difficult to bleed.

Sodium                           140     mmol/L        (133 – 147)

Potassium                        7.6    mmol/L        (3.5 – 5.0)

Urea                                 3.8     mmol/L        (2.5 – 7.5)

Creatinine                        90      µmol/L         (50-110)

Calcium                            0.9     mmol/L        (2.05 – 2.60)

Albumin                          40      g/L              (35 – 48)

Corrected Calcium           0.9     mmol/L        (2.05 – 2.60)

Full Blood Count.            All parameters within reference limits

Briefly indicate the possible cause of the abnormalities observed.

List, with reasons for their choice, any further tests that you may undertake on this sample to confirm your suspicions as to the cause.

• An 18 year old man with anorexia nervosa  was admitted, having collapsed after alcohol ingestion.  He weighed 29kg.  Plasma glucose concentration was <1 mmol/L and serum phosphate concentration 1.34 mmol/L.   He responded to intravenous dextrose.  After 2 days the plasma phosphate concentration fell to 0.45 mmol/L and after 4 days to 0.2 mmol/L.  Explain  the reasons  for this fall in phosphate.

• A 22 year old patient presents with pitting oedema and the following biochemical results.

Total Protein          39 g/L

Albumin                22 g/L

Cholesterol            17.5 mmol/L

Triglycerides          2.8 mmol/L

Briefly comment on these data. What are the most likely differential diagnoses? Suggest one further preliminary biochemical test to indicate a probable cause of the abnormalities seen.

• An 80 year old man with chronic obstructive airways disease and taking diuretics for associated cardiac failure presented with the following biochemistry results:-

Plasma potassium  2.6     mmol/L        (3.2-4.8)

Blood  pH              7.41                        (7.35-7.45)

PCO2                     10.3    kPa              (4.6 – 6.0)

HCO3          48      mmol/L        (24-32)

Briefly comment on these results and indicate the type or types of acid base disturbance present.

• A 36 year old married women complained of amenorrhoea for 2 months and has had several pregnancy test over  the preceding month. The GP asks for a prolactin measurement which is reported as 1240 mU/L.

The GP contacts you to ask for an interpretation of this result? Briefly indicate the questions that you would immediately ask him and indicate which further investigations you would wish to undertake on this specimen to help with your interpretation.

Calculations

• A patient is found to have a serum digoxin concentration of 3.9 µg/L. Digoxin administration was stopped and a further sample taken for analysis  97 hours later. If the half life of digoxin in the circulation is 38 hours what  would be the predicted  concentration of digoxin in this serum sample.

• An immunoassay for peptide-X involved extraction of 1mL of serum with 5mL of methanol. The methanol was evaporated to dryness under nitrogen and the residue re-dissolved in 250 µL of assay buffer. Aliquots (100 µL) of this solution were assayed in duplicate in an immunoassay calibrated, against non-extracted standards, to give a result in terms of femtomoles (fmol) per assay tube.  If the mean result of the duplicate assay of re-dissolved extract gave a result of 8 fmol/tube, and the average expected recovery for peptide-X extraction is 80%, calculate the concentration of peptide-X in the original sample in terms of picomoles per litre.

• Calculate the number of mmols of sodium reabsorbed in 24 hours by the kidneys of a healthy 70 Kg  man. Assume a daily urinary sodium excretion of 100 mmols. Clearly state the assumptions you make

14.   A screening  test for a disease has a diagnostic sensitivity of 95% and a diagnostic specificity of 98%. Calculate the negative predictive value of the test, and the efficiency of the test, given that testing of a randomly selected sample of 100,000 subjects revealed 100 false negative test results.

                          

1. Discuss the mechanisms and metabolic consequences of renal tubular dysfunction.
2. Discuss the various ways to determine glomerular filtration rates, and comment on the accuracy of the methods employed?
3. Write an essay on the mechanisms and consequences of hypo- and hyper-kalaemia.
4. “Parenteral nutrition is critically dependent upon a team approach if it is to be of benefit to the patient”. Discuss.