"...all doctors should be able to diagnose and treat nutritional deficiencies."

Royal College of Physicians. Nutrition and Patients: A Doctor's Responsibility. London 2002

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This page has been printed from the www.stewartnutrition.co.uk web site.


Nutritional Tests

Please read this before reviewing the table.

Laboratory tests of nutritional status are an important part of making a nutritional assessment.  However with the rapid increase in both the availability and popularity of many such tests it should be remembered that diagnosis is made from the history (of the person’s complaint, dietary intake and risk factors),  by clinical examination and then by appropriate use of laboratory or other tests.  Without the first two components no logical decision about the choice of tests and their interpretation can be made.
 
The tests listed in the two accompanying tables are those that are in most common use and the majority have been used in the National Diet and Nutrition Surveys, NDNS, over the last fifteen years.  The ranges quoted may vary from laboratory to laboratory.   Those who are taking blood samples should note that there may be specific instructions for the patient prior to the test as well as for sample collection and handling, laboratory analysis and interpretation of the result.  This is particularly true for trace elements, especially zinc (see www.izincg.org/pdf/English_brief2.pdf ) and vitamin A. 

Some tests may require the involvement of a regional or specialist laboratory, which may be in the NHS or in the private sector.  

Laboratory Tests of Nutritional Status - Minerals

Test and
Normal Range    
Likely Availability National Diet and Nutrition Survey
Local NHS Hospital Specialist Laboratory Tested in NDNS* Prevalence of deficiency on testing
 in NDNS populations
Anaemia - Haemoglobin
<12.0 – 16.0 g/dl - women
<13.0 – 17.0 g/dl - men
[WHO normal ranges]
Yes No Yes Anaemia in:
8% of women aged 19-64 yrs
10% of free-living elderly
40% of institutionalised elderly
Iron
Serum ferritin
<15.0 umol/l   
Yes No Yes 12% of women aged 19-49 yrs
8% of free-living elderly
10% of institutionalised elderly
Zinc
Plasma 10.0 - 20.0 umol/l
Possibly Yes Yes** 2% of free-living elderly
9% of institutionalised elderly
Manganese
Serum 9.0-25.0 umol/l
No Yes No Uncertain, probably rare
Copper
Serum <11.0 - 25.1 umol/l
Possibly Yes No Very rare but possible
Selenium
Plasma 0.29 - 0.91 umol/l
Unlikely Yes Yes** Severe deficiency is very rare but the prevalence of mild deficiency is unknown
Chromium
Serum 6.2 - 16.7  nmol/l
No Yes No Prevalence of mild deficiency appears to rise with increasing age
Iodine
Spot Urine >50 ug/l
Unlikely Possibly No Severe deficiency is very rare but the prevalence of mild deficiency is unknown
Magnesium
Serum 0.75 -  0.95  mmol/l
Red cell 2.08 - 3.0 mmol/l
Possible
Unlikely
Yes
Yes
No
No
Low if deficient or  metabolic disturbance
Low in some situations
Calcium
Bone Mineral Density
Serum <2.15 mmol/l
Yes
Yes
Yes
Yes
No
Yes**
Needed to diagnose osteoporosis
Serum value is not a measure of status.
Low levels are due to metabolic problems
Phosphate
Serum <0.8 mmol/l
Yes Yes No Rare unless very unwell
Sodium
Serum <135 mmol/l
Yes Yes No Deficiency is rare.  Low serum level indicates metabolic disturbance
Potassium
Serum <3.5 mmol/l
Yes Yes No Low serum levels usually indicate deficiency. Low intake is common in the elderly

*   National Diet and Nutrition Surveys of British Adults and the Elderly
** Measured in the NDNS of the elderly 65 years and over but not in adults


Laboratory Tests of Nutritional State – Vitamins

Test and  Normal Range Likely Availability National Diet and Nutrition Survey
Local NHS Hospital Specialist Laboratory Tested in NDNS* Prevalence of deficiency on testing
 in NDNS populations
Vitamin A

Serum retinol
0.7 – 2.5 mmol/l

Yes Yes Yes <1% of adults
<1% of all elderly
Vitamin B1-Thiamin
ETKAC^ >1.25
Possibly Yes Yes Increased enzyme activation coefficient
1% of adults
8% of free-living elderly
14% of institutionalised elderly
Vitamin B2 - Riboflavin
EGRAC^ >1.3
[clinical significance uncertain]
No Yes Yes Increased enzyme activation coefficient
66% of adults
41% of free-living elderly
35% of institutionalised elderly
Vitamin B3 No Possibly No Uncertain, but probably very low
Vitamin B5 No No No Deficiency is considered to be very rare
Vitamin B6
EAATAC^ >2.0
[clinical significance uncertain]
No Yes Yes Increased enzyme activation coefficient
11% of adults
Not measured in the elderly
Folate
Serum >7.0nmol/l
Red cell >350nmol/l
Yes
Yes
Yes
Yes
Yes
Yes
Serum folate low in:
< 1% or adults, 15% of the elderly
Red cell folate low in:
5% of adults, 29% of the elderly
Vitamin B12
Serum 118 - 750 pmol/l
Yes Yes Yes Serum vitamin B12 low in:
3% of adults
6% of free-living elderly
12% of institutionalised elderly
Biotin No Yes No Deficiency is rare but possible
Vitamin C
Plasma vitamin C
>11.0umol/l
Yes Yes Yes Plasma vitamin C low in:
4% of adults
14% of free-living elderly
41% of institutionalised elderly
Vitamin D
Plasma 25, hydroxy-
Vitamin D 25..0 - 200 nmol/l
Possibly Yes Yes Plasma vitamin D low in:
14% of adults
8% of free-living elderly
37% of institutionalised elderly
Vitamin E
Plasma alpha-tocopherol to cholesterol ratio
<2.25umol/mmol
Unlikely Yes Yes Vitamin E status was low in:
1% of adult men and 2% of adult women.
Not measured in the elderly
Vitamin K Assessed indirectly by INR Possibly No Status not assessed

^ Tests of vitamins B1, B2 and B6 involved erythrocyte enzyme activation and calculation respectively of:
Erythrocyte Transketolase Activation Coefficient, ETKAC
Erythrocyte Glutathione Reductase Activation Coefficient, EGRAC
Erythrocyte Aspartate Aminotransferase Activation Coefficient, EAATAC

* National Diet and Nutrition Surveys of British Adults and the Elderly

Availability of Tests of Nutritional Status in the UK

The availability of tests may vary considerably across the country but most important nutrients can be assessed either at a local hospital or through a specialist laboratory.   Details of specialist laboratories are given in the accompanying table.

Major NHS Nutritional Laboratories

Location Address
Birmingham Regional Laboratory for Toxicology
City Hospital
Dudley Road
Birmingham B18 7QH
Guildford Trace Element Laboratory
Centre for Clinical Science
School of Biological Sciences
University of Surrey
Guildford
 GU2 5XH
London Trace Metals Laboratory
Department of Clinical Biochemistry
King’s College Hospital
Denmark Hill
London SE25 9RS
London Medical Toxicology Unit
Avonley Road
New Cross
London SE14 5ER
Leeds Department of Biochemistry
Leeds General Infirmary
Great George Street
Leeds LS1 3EX
Liverpool Department of Clinical Chemistry
Royal Liverpool University Hospital
Prescot Street
Liverpool L7 8XP
Southampton Trace Element Unit
Clinical Biochemistry Department
Southampton General Hospital
Tremona Road
Southampton SO16 6YD
Scotland – Glasgow The Scottish Trace Element and Micronutrient Reference Laboratory
Department of Clinical Biochemistry
Glasgow Royal Infirmary
Glasgow G4 0SF
www.trace-elements.org.uk
[An interesting website with useful information about laboratory assessment of nutrients]
Wales – Cardiff Department of Medical Biochemistry and Immunology
University Hospital of Wales
Heath Park
Cardiff CF14 4XW

There are also private laboratories which also specialise in the assessment of essential nutrients see www.biolab.co.uk



Copyright Dr. Alan Stewart M.B.B.S.M.R.C.P. (UK)M.F. Hom.
47 Priory Street, Lewes, East Sussex. BN7 1HJ
Tel 01273 487003 Fax: 01273 487576