Download LACTATE/PYRUVATE RATIO Relevant disorders Related

DEPARTMENT OF CLINICAL CHEMISTRY
SHEFFIELD CHILDREN’S NHS FOUNDATION TRUST
LACTATE/PYRUVATE RATIO
Relevant disorders
For the differential diagnosis of elevated lactate only.
Related Metabolic Tests
Plasma lactate
CSF lactate
Indication for Test
Pyruvate should only be analysed when lactate is elevated to determine the
patients redox state.
Pyruvate is an end product of glycolysis. It can either be converted to lactate
under anaerobic conditions or transported into mitochondria to feed into the
Kreb’s cycle under aerobic conditions. Lactate dehydrogenase activity is high
in cells and maintains pyruvate and lactate at equilibrium, therefore when
pyruvate accumulates so does lactate. The lactate:pyruvate ratio is measured
to aid the differential diagnosis of lactic acidaemia. Pyruvate dehydrogenase
deficiency leads to the build up of pyruvate and therefore lactate, however the
ratio is normal. In mitochondrial disorders, while the lactate is increased,
pyruvate is less so and the ratio is abnormally high
Methodology
LDH
PYRUVATE + NADH <-------> LACTATE + NAD
Pyruvate in the presence of excess NADH and LDH at pH 7 is converted to
lactate and NAD. The fall in concentration of NADH is estimated by measuring
its absorbance at 340 nm.
Sample requirements
Blood or CSF. Samples HAVE to be mixed with Perchloric Acid.
Pre weigh a plain tube.
Add a known volume of Perchloric acid (PCA) 5.1% v/v – minimum 0.5ml
Weigh tube with PCA.
Make a note of the weight.
DEPARTMENT OF CLINICAL CHEMISTRY
SHEFFIELD CHILDREN’S NHS FOUNDATION TRUST
Immediately after taking the sample add an equal volume of whole blood or
CSF to the tube containing the PCA (collect blood initially into a Lithium
heparin tube).
Mix well and transport on ice to the lab without delay.
Weight the tube again.
Note weight of sample added to the tube (this should equal the amount of acid
added).
Separate and store the clear supernatant at -20 ˚C.
Please note the weights on the laboratory request form.
Lactate should also be requested on this sample.
Transport information/Contact details
Transport the sample DEEP FROZEN. Sample MUST arrive at Clinical
Chemistry, Sheffield Children’s Hospital frozen.
Department of Clinical Chemistry
Sheffield Children’s NHS Foundation Trust
Western Bank, Sheffield
S10 2TH, UK
Jennifer Watkinson (BMS 3)
0114 2717445
Turn Around Time
5 – 14 days
Reference Ranges
Pyruvate analysis may be useful in the differential diagnosis of lactic
acidaemia and should only be analysed if the lactate is elevated. The ratio of
lactate to pyruvate can be calculated to determine the redox state, upper limit
of normal approx 30 but this may be slightly higher in neonates and lower in
older children. An elevated redox state may indicate a primary disorder eg.
respiratory chain disorder or a secondary disturbance such as
hypoxia/ischaemia. In pyruvate dehydrogenase deficiency the ratio will be
normal or reduced.
References
•
Olsen C. Clin Chim Acta 33 (1971) 293