Blood draw
Calcium (Albumin-Corrected)
Albumin-corrected calcium; calcium balance.
€ 32,00
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Vitamins, minerals and amino acids · Blood
Calcium (albumin-corrected)
Calculated estimate of the free, active calcium from calcium and albumin; mainly useful when albumin is abnormal.
At a glance
- Measured in blood
- In 1 test panel
- No special preparation
Explanation
Calcium (albumin-corrected): what is measured?
This value is not measured but calculated by the laboratory from two measurements: total calcium and the protein albumin. A large part of the calcium in the blood is bound to albumin; only the free (ionized) part is active. If albumin is low, total calcium is also lower, while free calcium can be normal. The calculation estimates how much free, active calcium there is. The result is therefore a different number from total calcium and cannot be compared with a total calcium result.
What can it detect?
- Calcium that is too high (hypercalcemia) that only becomes visible after correction when albumin is low
- A low total calcium that turns out normal after correction, because only the albumin is low
Result
What does the result mean?
Calcium (albumin-corrected) too high
A raised corrected calcium can mean that the active calcium is too high. The causes are the same as for a raised total calcium: usually an overactive parathyroid gland (primary hyperparathyroidism), sometimes high doses of vitamin D or calcium, thiazide diuretics or lithium. With a low albumin, however, correction formulas sometimes calculate the calcium too high, depending on the measurement method for albumin. A slightly raised result is therefore not always a truly raised calcium. Rarely: a malignant condition, such as metastases in the bone or multiple myeloma (Kahler's disease, a bone marrow disease).
Calcium (albumin-corrected) too low
A low corrected calcium fits a truly low calcium (hypocalcemia), for example due to a deficiency of vitamin D or magnesium, reduced kidney function, poor absorption in the intestine or an underactive parathyroid gland. Because the correction already takes the albumin into account, a low albumin is no longer an explanation here. With a high albumin, however, the formula can estimate the calcium somewhat too low. Symptoms that may go with it are tingling in the fingers and around the mouth, muscle cramps and muscle twitches.
After an abnormal result
With an abnormal corrected calcium, the GP repeats calcium and albumin and, if needed, measures parathyroid hormone (PTH), phosphate, kidney function and vitamin D. When the calculation is in doubt, for example with a strongly lowered albumin, free calcium can be measured directly in hospital.
Reliability
How reliable is the test?
Corrected calcium is a calculated estimate of the free, active calcium and less accurate than a direct measurement of free (ionized) calcium; correction formulas sometimes calculate the value too high. Because the outcome approximates free calcium, the numbers and limit values differ from those for total calcium and cannot be compared with them. With a normal albumin, the calculation adds little beyond the measured total calcium. The outcome depends strongly on the formula and the measurement method for albumin: Dutch research at ten hospital laboratories showed that commonly used formulas from the literature overcorrect, and advises each laboratory to use its own correction factor. When in doubt, a direct measurement of free (ionized) calcium in hospital gives more certainty.
What can affect the result?
- Laboratories use different formulas; some estimate free calcium, others convert total calcium to a normal albumin. Results from different laboratories, and an earlier total calcium result, can therefore not be compared with this result.
- With the bromocresol purple albumin method, the common formulas overestimate calcium, especially with a low albumin.
- With a very low albumin, kidney disease or dialysis, the calculation is less reliable.
- Anything that affects total calcium, such as a tourniquet left on too long, vitamin D, calcium tablets and thiazide diuretics, also carries over into the calculated value.
Who it is for
Who is the test useful for?
Useful for
Useful when albumin is abnormal, for example with liver or kidney disease, malnutrition or after a long illness, and as an addition with an abnormal total calcium. In healthy adults with a normal albumin, the calculation adds little beyond the standard calcium.
How common is it?
A clearly low albumin, where the correction makes the most difference, is uncommon in healthy adults. In one Dutch hospital laboratory, the share of corrected calcium results above the reference value fell from 14 to 4 percent after switching to its own correction factor. The chosen formula therefore partly determines how often a raised calcium is found.
Laboratoriumgeneeskunde (NVKC, 2018)
Drawbacks and risks
- A formula that overcorrects can show a normal calcium as raised; this can lead to unnecessary worry and unnecessary testing of the parathyroid gland.
Get tested
Calcium (albumin-corrected): test panels
Calcium (albumin-corrected) is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.
Evidence
Sources
This explanation is based on Dutch guidelines and independent information. It is general information, not a diagnosis. Discuss an abnormal result with your GP.
More about risks and results- Laboratoriumgeneeskunde (NVKC, 2018): Keuze van correctiefactoren voor totaal calcium in relatie tot de analytische methode voor albumine
- Nederlandse Internisten Vereniging, Het Acute Boekje: Hypercalciëmie
- Nederlandse Internisten Vereniging, Het Acute Boekje: Hypocalciëmie
- NVKC, allesovertesten.nl: Calcium
- Medlab Stein, leistungsverzeichnis: Calcium, korrigiertes (Albumin)
More explanations
Other tests: Vitamins, minerals and amino acids
- AC/FC ratio
- Acylcarnitine
- Alanine
- Antibodies against intrinsic factor
- Arginine
- Calcium
- Carnitine, free
- Carnitine, total
- Coenzyme Q10
- Copper
- Folic acid
- Glutamic acid (urine)