Practice Points
- LDH testing is only useful for hemolytic anemia and cell growth disorders; there is little need for it in family practice.
- Creatine kinase is a useful test in patients with a high index of suspicion for muscle disease; it is no longer needed for monitoring asymptomatic patients on statins.
- Serum Ferritin is a useful iron status test where hemochromatosis or hypoferritinemia are suspected as a cause of symptoms; it is not useful in patients with normal hemoglobin and normal MCV/MCHC.
- Blood urea is not a useful test to measure kidney function in stable patients.
- These four tests are probably unnecessary unless there is a clinical indication for their use, as above.
Volume of LDH Testing in General Practice by Doctor
Indication: hemolytic anemia and cell growth disorder
Volume of Creatine Kinase Testing in General Practice by Doctor
Indication: high index of suspicion in muscle disease
Volume of Ferritin and Iron Saturation Testing in General Practice by Doctor
Indication: iron status
Volume of Urea Testing in General Practice by Doctor
Not indicated in stable kidney function
Combined Cost of the Above Tests, By Ordering Doctor in Family Practice
1 April 2015 to 31 March 2016
It is understood that a proportion of these tests are necessary, but they are not indicated in many cases.
Conclusion
- A minority of doctors order the majority of these four laboratory tests.
- These tests are best ordered for appropriate clinical indications.
- They are not useful as screening tests.
- Individual tests may be low cost – LDH, creatine kinase, and urea are $2 each, and ferritin $10 – but the costs mount as the volume of testing increases.