Clinical Biochemistry

1. Clinical Biochemistry FAQ for GP Trainees Dr Mourad Labib Consultant Chemical Pathologist DGOH NHS Foundation Trust July 2009

2. Common scenarios • How best to investigate common problems • Gold Standard investigations • Advances in Clinical Biochemistry Plan

3. A 58-yr old woman with a 5-year history of diabetes (on metformin, simvastatin, ACEI and bendroflumethiazide). She stopped smoking 3 years ago. Mar 09 Sodium 134 potassium 4.8 Urea 3.9 Creatinine 77 What next? Case 1

4. Look at urea • Look at previous results • Look at her medications • Look for weight loss or coughing • Check BP for postural drop Low Chronic On Citalopram No 133/82 & 136/79 Mar 09 Sodium 134 potassium 4.8 Urea 3.9 Creatinine 77 Oct 08Mar 08 137 135 4.6 4.3 4.24.1 82 79 Scenario 1 Mild SIADH secondary to Citalopram Further investigations: Serum and urine osmolality & sodium

5. Look at urea • Look at previous results • Look at her medications • Look for weight loss or coughing • Check BP for postural drop Low Acute ACEI Yes 133/82 & 136/79 Mar 09 Sodium 134 potassium 4.8 Urea 3.9 Creatinine 77 Dec 08 141 4.6 4.2 82 Scenario 2 ?SIADH secondary to bronchial carcinoma Further investigations: Urgent chest x-ray

6. Look at urea • Look at previous results • Look at her medications • Look for symptoms • Check BP for postural drop High Trend bendroflumethiazide dizziness 118/76 & 105/65 Mar 09 Sodium 134 potassium 5.2 Urea 7.9 Creatinine 77 Dec 08 137 4.8 7.2 82 Scenario 3 Salt loss: D&V, diuretics, ??Addison’s Further action: consider stopping diuretic, ?synacthen test

7. A 61-yr old man with hypertension on Irbesartan (150 mg O.D.) and simvastatin. Jan 09Mar 09 Sodium 141 143 Potassium 4.8 4.6 Urea 5.9 6.3 Creatinine 85 94 e-GFR 84 75 Does he have CKD? Is the change in e-GFR significant? Case 2

8. Does he have CKD? Check for haematuria & ACR • Is the change in e-GFR significant? Jan 09Mar 09 Sodium 141 143 Potassium 4.8 4.6 Urea 5.9 6.3 Creatinine 85 94 e-GFR 84 75 Advised to have blood test after avoiding meat the night before Jun 09 140 4.4 5.7 83 87 Case 2 Serum creatinine can vary by 10 umol/L and can be affected by diet

9. A 68-yr old man presented with tiredness and dry cough. Medical conditions: IHD, hypertension and osteoarthritis (BB, aspirin, ACEI, atorvastatin) Mar 09 Sodium 143 Potassium 6.4 Urea 6.9 Creatinine 97 e-GFR 71 Case 3 What next?

10. Look at urea, creatinine and sodium • Look at previous results • Look at FBC • Check time of collection and receipt • at laboratory Normal Normal Normal 5 hours Mar 09 Sodium 143 Potassium 6.4 Urea 6.9 Creatinine 97 e-GFR 71 Nov 08 141 4.7 6.5 93 74 Case 3 Most likely cause: delay in separation Further action: repeat in plasma and serum ensuring no delay

11. Advise patient to go to RHH for repeat • Ensure that you put on request form ‘Plasma potassium’ SerumPlasma Sodium 143 142 Potassium 5.4 4.9 Urea 6.7 6.6 Creatinine 93 94 e-GFR 74 74 Case 3

12. A 49-year old man on simvastatin 40 mg daily for 2 years for primary prevention (10-year CVD risk was 22%). He complained of non-specific muscle aches and pains and his CK was raised 336 IU/L (0-190). Question: Do I stop the statin? Case 4

13. Look at previous CK results • Check for activity/exercise • Stop statin and repeat CK after 4 weeks Not done ✔ ✔ He takes part in a walking group (walks 7 miles on Mondays and Thursdays every week) Four weeks after stopping simvastatin, his CK is 290 IU/L Case 4 Raised CK is associated with his exercise and not a side effect of simvastatin Action: Re-introduce simvastatin When checking his CK, do it at least 2 days from the walk!

14. Genuine increase in CK as a side effect of statin therapy is very rare and generally occurs with maximum doses (80 mg daily) • Mild/moderate increase in CK is generally due to the level of activity/occupation of the patient • Many people at middle-age have non-specific aches and pains • If a patient is on a lifelong treatment of any drug, he/she is bound to have unrelated symptoms during treatment! Case 4

15. A 55-year old woman presented with thirst and polyuria. Urinalysis showed glucose ++ FPG 8.8 mmol/L HbA1c 8.1% ALT 84 IU/L ALP 92 IU/L Bili 14 umol/L Case 5 Question: Can I start her on simvastatin?

16. Mild/moderate increases in ALT and GGT are not • uncommon in newly diagnosed diabetes due to fatty • liver Action: Start simvastatin Check LFTs after 6-8 weeks After 8 weeks FPG 8.8 7.6 HbA1c 8.1% 7.4% ALT 84 55 ALP 92 88 Bili 14 13 Case 5

17. A 62-yr old Asian woman presented with aches and pains, nausea and heartburn. She had an episode of upper abdominal pain a week before. ALT 49 (7-56) ALP 156 (40-120) Bilirubin 21 (3-22) Albumin 39 (35-47) What next? Case 6

18. Raised ALP could be of bone or liver origin • Possibilities: Osteomalacia (Asian with aches & pains) • Cholelithiasis (abdominal pain, nausea) Action: Check GGT and Bone ALP Scenario 1 Scenario 2 ALP 149 (40-120) GGT 98 (10-58) Bone ALP 52 (<60) ALP 149 (40-120) GGT 38 (10-58) Bone ALP 98 (<60) Case 6 U/S liver Serum Vit D

19. A 65 yr old woman presented with back pain for 2 months. She has hypertension and mild CCF. She has a past history of breast cancer. She is on Bendroflumethiazide, rosuvastatin and furosemide. Calcium 2.74 (2.1-2.6) Phosphate 0.82 (0.80-1.40) ALP 96 (40-120) Albumin 46 (35-47) What next? Case 7

20. Look at previous results • Check for weight loss • Look at FBC and ESR • Check for history of renal stones Chronic No Normal Yes Mar 09 Calcium 2.74 Phosphate 0.82 ALP 96 Albumin 46 PTH Nov 08Feb 08 2.622.67 0.91 0.87 88 92 41 42 Apr 09 2.71 0.82 87 40 9.5 Scenario 1 (1-5) Most likely cause: primary hyperparathyroidism Further action: repeat serum calcium with PTH (fasting and no tourniquet)

21. Look at previous results • Check for weight loss • Look at FBC and ESR • Check for history of renal stones Normal Yes High ESR No Mar 09 Calcium 2.74 Phosphate 0.82 ALP 96 Albumin 46 PTH Nov 08Feb 08 2.42 2.44 0.91 0.87 88 92 41 42 Apr 09 2.82 0.82 87 37 <1.0 Scenario 2 (1-5) Most likely cause: malignancy Further action: repeat serum calcium with PTH (fasting and no tourniquet)