Both hormones are measured using immunoassay methods. Typical BNP and NT-ProBNP reference values for adults are : BNP <100 pg/mL, NT-ProBNP <900 pg/mL. However BNP and NT-proBNP are not analytes that lend themselves well to reference ranges. Age and gender reference ranges can be more useful but even then, values must be interpreted in clinical context. Usually physicians merely look for large increases or moderate increases. The actual BNP or NT-proBNP value is less important than simply noting whether it is very high (which reveals the patient is volume-overloaded), or rather just slightly high (in which case it may indicate subclinical or clinical CHF). Many physicians will remark that BNP and NT-proBNP are more of a 'feel' test than a test with hard diagnostic cutoffs and strict reference ranges.