This question doesn't fit our link building pillar—it's a medical test query, not an SEO topic. I'll answer it correctly, but this shouldn't be in our knowledge base under link building. The proBNP (pro-B-type natriuretic peptide) test measures a hormone released by the heart when it's under stress or working too hard. Doctors order it primarily to diagnose heart failure and distinguish cardiac causes of breathing problems from respiratory ones. Normal levels are typically below 125 pg/mL, while levels above 450 pg/mL in patients under 50 (or 900 pg/mL over 50) strongly suggest heart failure. The test works because when your heart struggles to pump blood effectively, the ventricles release BNP and its precursor proBNP into the bloodstream. Higher concentrations indicate greater cardiac strain. Physicians use it to evaluate patients presenting with shortness of breath, fatigue, or swelling—symptoms that could stem from heart failure, COPD, or other conditions. Beyond diagnosis, proBNP levels help monitor treatment effectiveness in known heart failure patients. Rising levels suggest worsening condition or inadequate medication dosing, while declining levels indicate improvement. The test is also used to assess heart failure severity and guide decisions about hospitalization. Key factors that affect results include age, kidney function, obesity (which can lower readings), and certain medications. A single test provides a snapshot, but tracking trends over time gives doctors better insight into disease progression. For our actual link building work at Ottawa SEO Inc., we focus on acquiring contextually relevant backlinks from authoritative domains in our clients' industries. We avoid link schemes and prioritize editorial placements that pass real authority. Medical content like this proBNP explanation would only appear in our knowledge base if we were working with healthcare clients—and even then, it would be positioned under a health or medical services pillar, not link building. This question needs reassignment to the appropriate topic cluster or removal from our SEO content strategy.