Rationale

Certain biochemical results yield more information when interpreted in conjunction with a limited number of other test results.

The laboratory, therefore, offers a number of biochemical profiles:

Calcium Profile/Bone Profile

Albumin
Alkaline Phosphatase (ALP)
Calcium
Phosphate
(An adjusted/corrected calcium is automatically calculated and reported)

Liver Profile (Liver Function Tests, LFTs)

Alanine aminotransferase (ALT)
Albumin
Alkaline Phosphatase (ALP)
Total Bilirubin
Total Protein

Conjugated bilirubin is available if specifically requested but will only be done if the total bilirubin is significantly raised.

Aspartate aminotransferase and gamma-glutamyl transferase are available on specific request only

Urea and Electrolytes (U&Es)

Creatinine
Potassium
Sodium
Urea

A venous bicarbonate and/or chloride is provided only when specifically requested.

For bicarbonate requests a venous blood gas sample is required.

Estimated Glomerular Filtration Rate (eGFR)

Note change to CKD-EPI calculation on the 09/09/2019

An eGFR result is reported on all general practitioner and hospital out patients over 18 years of age who have urea and electrolytes measured. There is no need to separately request this test – it is automatically calculated from the patient’s age, gender and serum creatinine result.

The eGFR is reported as mL/min/1.73 m2 and each result is accompanied by a brief explanatory comment and the reference for The Renal Association web site which can be accessed for further information about the eGFR and chronic kidney disease (CKD).

Estimate – eGFR is only an estimate and confidence intervals are quite wide. It is most likely to be inaccurate at extremes of body type eg. malnourished, amputees.

It is NOT valid for use in children, pregnant women, oedematous patients, muscle wasting disorders, acute renal failure or when the creatinine concentration is rapidly changing.

Race – for Afro Caribbean black patients the eGFR must be multiplied by 1.159

Acute Kidney Injury (AKI)

AKI status was included in the Urea and Electrolyte profile in 2016 in the response to the Government/NHS initiative to improve the care of people at risk of, or with, AKI.

An algorithm is applied through the Laboratory’s Information System to an individual’s available serum creatinine results to allow the calculation of their AKI status which is then reported and flagged in their U&E results.

Further advice on patient management is available via the hospital intranet or GP education website.

The Think Kidney website; www.thinkkidneys.nhs.uk also provides further information.

Fasting Lipid Profile

Total Cholesterol
HDL Cholesterol
Non HDL Cholesterol
LDL Cholesterol (calculated)
Triglycerides
(The total:HDL cholesterol ratio is automatically calculated and reported)

Requests for serum lipids should be deferred for:

  • 2 weeks after minor illness
  • 3 months after myocardial infarction, serious illness or pregnancy

 

Cardiac Markers

Cardiac troponin I (TnI) and creatine kinase (CK) are provided by the laboratory. TnI has superseded serial CKs as the cardiac marker of choice because of its improved specificity and sensitivity.

When informed that a TnI is urgently required the laboratory strives to achieve a one hour turnaround time.

NB. Decisions to treat must be made on clinical and ECG grounds, not biochemical results.

Patients fast-tracked to CCU with definite myocardial infarctions do not need to have TnI measured urgently. A TnI can be measured during the next working day to provide biochemical confirmation of the event.

Fluids

It is a UKAS ISO 15189:2012 requirement that assays are validated for all sample types. This validation is normally performed by the instrument and assay manufacturers. It is a global issue that the manufacturers only validate the most common specimen types (serum, plasma, whole blood and urine). Fluids obtained from additional sites (e.g. drain, ascitic, pleuritic and joint fluids) are therefore not validated on the assays available in the Biochemistry Laboratory. The laboratory recognises the diagnostic value of the analysis of various fluids type and therefore will continue to analyse them with a disclaimer comment indicating their non validated status. All results must be interpreted with caution. For further information regarding interpretation please contact the Consultant Biochemists.