Specimen requirement

Balanced heparin syringe  

(*Please note that different brands of syringe with different size and heparin content are used in NTEC hospitals.)

Minimum blood volume: 0.6 mL (using 1 mL syringe containing 30 IU balanced lithium heparin)

Minimum blood volume: 1.6 mL (using 3 mL syringe containing 80 IU balanced lithium heparin)

Authorisation code required

No

24 Hr available service

Yes

Precaution

Blood Taking Procedure

1. Appropriate volume of blood should be collected anaerobically in a special balanced heparin syringe. (Collect 0.6 mL blood for 1 mL syringe and 1.6 mL for 3 mL syringe so that the final concentration of the balanced heparin in sample is 50 IU/mL.)
    
2. Dispose the needle, tap syringe to move air bubble to the top and slowly advance plunger to expel air from sample, and then re-cap the syringe with a cap.
    
3. To ensure thorough mixing of blood with heparin, hold syringe in hand and rotate back and forth for 20 to 30 sec.
   
   
4. Send the blood sample in ice bath to the laboratory immediately for analysis.

Avoid using sample collection devices containing EDTA, citrate, oxalate, and fluoride anticoagulants. These anticoagulants have a significant effect on blood pH and ionised calcium.

Avoid using excessive levels of heparin anticoagulants. Excessive levels of heparin anticoagulants cause calcium-heparin chelation and falsely decrease calcium levels.

Method

Ion selective electrode

Reference interval

(Source: Lentner C ed. Geigy Scientific Tables 3: 82 - 83, 1984. 8th Edition, Ciba - Geigy Ltd.)

Clinical indication

Diagnosis of hypercalcaemia and hypocalcaemia.

Calcium occurs in plasma as ionised, complexed and protein bound forms. It can be measured as total calcium, ionised calcium, or corrected calcium (in which total calcium is corrected, usually in relation to the patient’s albumin level).      

Ionised calcium is required if complexed calcium is likely to be very high (e.g. during massive transfusion), if pH is abnormal or if an abnormality in calcium is marginal.

Result interpretation

Elevated ionised calcium levels are detected in patients with primary / tertiary hyperparathyroidism; malignancy especially lung, multiple myeloma, kidney, bony metastases; sarcoidosis; vitamin D or vitamin A toxicity.    

Decreased ionised calcium levels are detected in patients with hypoparathyroidism, renal failure, osteomalacia or rickets.

Measurement of uncertainty

See table.

Frequency of measurement

Daily