Lab note : Transport plasma at ambient temp, but freeze if it is likely to take more than 3 days to reach LabPlus.
Sample stability:
-
3 days at 20-25 o C
-
6 days at 2-8 o C
-
24 months at -20 o C
Units: pmol/L
Ruling out heart failure:
A level <35pmol/L strongly rules out heart failure (any age).
Ruling in heart failure:
The level which strongly supports heart failure depends on age:
| <50years |
>53 pmol/L
|
| 50-75years |
>106 pmol/L
|
| >75 years |
>212 pmol/L |
Note that some clinical guidelines use alternate units . To convert between different units, use the following formulae:
To change from pg/mL to pmol/L
Multiply by 0.118
To change from ng/L to pmol/L
Multiply by 0.118
To change from pmol/L to pg/mL
Multiply by 8.457
To change from pmol/L to ng/L
Multiply by 8.457
Uncertainty of measurement: 12% at a level of 9
7% at a level of 40 and higher
Principle : Sandwich type immunoassay with chemiluminescence detection
Assay : Roche ProBNP II
Analyser : Cobas e801
BNP is a hormone secreted by the overloaded ventricle of the heart. Our lab measures NT-proBNP, which is a byproduct of the secretion of BNP. It differs from BNP in clearance, analytical characteristics and reference intervals.
Besides heart failure, NT-proBNP may be elevated in renal impairment, atrial fibrillation, LVH, valvular heart disease, post-myocardial infarction, pulmonary hypertension and in the elderly. NT-proBNP tends to decrease with increased BMI, hypothyroidism, diuretic treatment, vasodilators and ACE-inhibitors.
Even in stable heart failure, there is a lot of within-person biological variability, i.e. a patient's NT-proBNP result can change significantly from week to week without a significant change in clinical status. An increase or decrease of up to 98% of baseline may be seen due to this biological variation.
Generally it is not helpful to repeatedly measure NT-proBNP to monitor acute response to treatment. The test is expensive and should be dictated by clinical need and after consultation with a physician or cardiologist.
Emails to chemicalpathologist@adhb.govt.nz will receive priority attention from the on-call chemical pathologist.
If the query concerns a specific patient please include the NHI number in your email.
If email is not a suitable option, please contact the on-call chemical pathologist via Lablink (Auckland City Hospital ext. 22000 or 09-3078995).
Individual chemical pathologists may be contacted but will not be available at all times.
After-hours : contact Lablink (Auckland City Hospital ext. 22000 or 09-3078995) or hospital operator for on duty staff after hours.
Dr Samarina Musaad (Clinical Lead) : SamarinaM@adhb.govt.nz ext. 22402
Dr Cam Kyle: CampbellK@adhb.govt.nz ext 22052
Dr Weldon Chiu: WeldonC@adhb.govt.nz ext. 23427
Dr Campbell Heron: CHeron@adhb.govt.nz ext. 23427
Dr Sakunthala Jayasinghe: Sakunthala@adhb.govt.nz ext. 23427