Clinical BiochemistryClinical Biochemistry

FAQ for GP Trainees

Dr Mourad LabibConsultant Chemical Pathologist

DGOH NHS Foundation Trust

July 2009

PlanPlan

Common scenarios

How best to investigate common problems

Gold Standard investigations

Advances in Clinical Biochemistry

Case 1Case 1A 58-yr old woman with a 5-year history of diabetes (on metformin, simvastatin, ACEI and bendroflumethiazide). Shestopped smoking 3 years ago.

Mar 09

Sodium 134potassium 4.8Urea 3.9Creatinine 77

What next?

Scenario 1Scenario 1• Look at urea• Look at previous results• Look at her medications• Look for weight loss or coughing• Check BP for postural drop

Low

Mar 09

Sodium 134potassium 4.8Urea 3.9Creatinine 77

Oct 08 Mar 08

137 135 4.6 4.3 4.2 4.1 82 79

ChronicOn Citalopram

No133/82 & 136/79

Mild SIADH secondary to Citalopram

Further investigations: Serum and urine osmolality & sodium

Scenario 2Scenario 2• Look at urea• Look at previous results• Look at her medications• Look for weight loss or coughing• Check BP for postural drop

Low

Mar 09

Sodium 134potassium 4.8Urea 3.9Creatinine 77

Dec 08

141 4.6 4.2 82

AcuteACEI

Yes

133/82 & 136/79

?SIADH secondary to bronchial carcinoma

Further investigations: Urgent chest x-ray

Scenario 3Scenario 3• Look at urea• Look at previous results• Look at her medications• Look for symptoms • Check BP for postural drop

High

Mar 09

Sodium 134potassium 5.2Urea 7.9Creatinine 77

Trend

Dec 08

137 4.8 7.2 82

bendroflumethiazide dizziness

118/76 & 105/65

Salt loss: D&V, diuretics, ??Addison’s

Further action: consider stopping diuretic, ?synacthen test

Case 2Case 2

A 61-yr old man with hypertension on Irbesartan (150 mg O.D.) and simvastatin.

Jan 09 Mar 09

Sodium 141 143Potassium 4.8 4.6Urea 5.9 6.3Creatinine 85 94e-GFR 84 75

Does he have CKD?Is the change in e-GFR significant?

Case 2Case 2

• Does he have CKD? Check for haematuria & ACR

• Is the change in e-GFR significant?

Jan 09 Mar 09

Sodium 141 143 Potassium 4.8 4.6 Urea 5.9 6.3 Creatinine 85 94 e-GFR 84 75

Jun 09

140 4.4 5.7 83 87

Advised to have

blood test after

avoiding meat the

night before

Serum creatinine can vary by 10 umol/L and can be affected by diet

Case 3Case 3A 68-yr old man presented with tiredness and dry cough.Medical conditions: IHD, hypertension and osteoarthritis (BB,aspirin, ACEI, atorvastatin)

Mar 09

Sodium 143Potassium 6.4Urea 6.9Creatinine 97e-GFR 71

What next?

Case 3Case 3• Look at urea, creatinine and sodium• Look at previous results• Look at FBC• Check time of collection and receipt at laboratory

NormalNormalNormal5 hours

Mar 09

Sodium 143Potassium 6.4Urea 6.9Creatinine 97e-GFR 71

Nov 08

141 4.7 6.5 93 74

Most likely cause: delay in separation

Further action: repeat in plasma and serum ensuring no delay

Case 3Case 3

Serum Plasma

Sodium 143 142Potassium 5.4 4.9Urea 6.7 6.6Creatinine 93 94e-GFR 74 74

• Advise patient to go to RHH for repeat• Ensure that you put on request form ‘Plasma potassium’

Case 4Case 4

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 4Case 4• 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

✔

✔

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!

Case 4Case 4

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 5Case 5

A 55-year old woman presented with thirst and polyuria. Urinalysis showed glucose ++

FPG 8.8 mmol/LHbA1c 8.1%

ALT 84 IU/LALP 92 IU/LBili 14 umol/L

Question: Can I start her on simvastatin?

Case 5Case 5• Mild/moderate increases in ALT and GGT are not uncommon in newly diagnosed diabetes due to fatty liver

Action: Start simvastatinCheck LFTs after 6-8 weeks

FPG 8.8 7.6HbA1c 8.1% 7.4%

ALT 84 55ALP 92 88Bili 14 13

After 8 weeks

Case 6Case 6A 62-yr old Asian woman presented with aches and pains,nausea and heartburn. She had an episode of upperabdominal pain a week before.

ALT 49 (7-56)ALP 156 (40-120)Bilirubin 21 (3-22)Albumin 39 (35-47)

What next?

Case 6Case 6

• 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

ALP 149 (40-120)GGT 98 (10-58)Bone ALP 52 (<60)

Scenario 1

U/S liver

Scenario 2

ALP 149 (40-120)GGT 38 (10-58)Bone ALP 98 (<60)

Serum Vit D

Case 7Case 7A 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?

Scenario 1Scenario 1• Look at previous results• Check for weight loss• Look at FBC and ESR• Check for history of renal stones

ChronicNoNormalYes

Mar 09

Calcium 2.74 Phosphate 0.82 ALP 96 Albumin 46 PTH

Nov 08 Feb 08

2.62 2.67 0.91 0.87 88 92 41 42

Most likely cause: primary hyperparathyroidism

Further action: repeat serum calcium with PTH (fasting and no tourniquet)

Apr 09

2.71 0.82 87 40 9.5 (1-5)

Scenario 2Scenario 2• Look at previous results• Check for weight loss• Look at FBC and ESR• Check for history of renal stones

NormalYesHigh ESRNo

Mar 09

Calcium 2.74 Phosphate 0.82 ALP 96 Albumin 46 PTH

Nov 08 Feb 08

2.42 2.44 0.91 0.87 88 92 41 42

Most likely cause: malignancy

Further action: repeat serum calcium with PTH (fasting and no tourniquet)

Apr 09

2.82 0.82 87 37 <1.0 (1-5)