Total Calcium & Corrected Calcium & Ionized Calcium

من قبل Yasser Ahmed Taha‏ في تحاليل طبية‏ ·

Total calcium consists of: 1-  free or ionized calcium (50%)

2- calcium bound to protein (40-45%) principally albumin

3-  calcium complexed to anions (5-10%), e.g. citrate, lactate, bicarbonate.

Total calcium level does not give an indication of what is available at the cellular level. Ionized calcium (iCa) is the form of calcium that is readily available to cells, and measurement of iCa is a more accurate reflection of the physiological calcium state. Measurement of ionized calcium requires instrumentation with ion-specific electrodes. Unlike total calcium, ionized calcium is unaffected by albumin concentration, but it is affected by acid-base balance

 

 

Calculation of Corrected calcium :

 

Because calcium binds to albumin and only the unbound (free or ionized) calcium is biologically active, the serum level must be adjusted for abnormal albumin levels.

For every 1-g/dL drop in serum albumin below 4 g/dL, measured serum calcium decreases by 0.8 mg/dL. Therefore, to correct for an albumin level of less than 4 g/dL, one should add 0.8 to the measured value of calcium for each 1-g/dL decrease in albumin. Without this correction, an abnormally high serum calcium level may appear to be normal

 

example :

A patient with a serum calcium level of 10.3 mg/dL but an albumin level of 3 g/dL appears to have a normal serum calcium level. but, when corrected for the low albumin, the real serum calcium value is 11.1 mg/dL (4 – 3 X 0.8 + 10.3 ), a more obviously abnormal level. Corrected calcium can be calculated using the following formula:

 

Normal range of calcium = 8.5 – 10.5 mg/dl Or 2.2 – 2.5 mmol/l

convertions :

 

Calcium (mg/dL) x 0.25 = calcium (mmol/L)

(Albumin (g/dL) x 10 = albumin (g/L)

 

Corrected Calcium ( mg/dl) = ([4 – plasma albumin in g/dL] X 0.8 + serum calcium mg/dl)

 

الخلاصة  : لما نيجى نقيص الكالسيوم ويطلع طبيعى ونقيص الالبومين ويطلع الالبومين غير طبيعى ( اقل من 4 ) يبقى لازم نستخدم معادلة تصحيح الكالسيوم عشان الكالسيوم بعد المعادلة هيعطيك المعدل الحقيقى للكالسيوم ( لان الكالسيوم عند قياسة بدون تصحيح بيقل 0.8 مع كل 1 جرام نقص فى الالبومين

 

 

Calculated Free Calcium ( ionized calcium ) in mg/dl :

 

Normal range of calcium = 8.8 – 10.5 mg/dl    Or   2.2 – 2.55 mmol/l

Normal range ionized calcium = 4.5 – 5.6 mg/dL   Or   1.1-1.4 mmol/L

 

convertions :

Calcium (mg/dL) x 0.25 = calcium (mmol/L)

Albumin (g/dL) x 10 = albumin (g/L)

 

ionized calcium ( mg/dl ) =( total calcium ( mg/dl ) – Albumin ( g/dl ) + 4) / 2