Lipoprotein(a) May Be Falsely Lowered When Troponin T is Elevated in Patients with Ischaemic Heart Disease During Acute Admissions

Background: It is unclear whether lipoprotein(a) – Lp(a) – concentration is affected during acute admissions in patients with ischaemic heart disease (IHD). We investigated whether Lp(a) concentration was acutely affected in patients admitted to hospital with elevated serum troponin T concentration. Methods: We analysed the variability of serum Lp(a) concentrations and its correlation with high levels of troponin T in patients with IHD who were admitted to the cardiology department in Changi General Hospital in Singapore over a year. Elevated Lp(a) was defined as ≥120 nmol/l. Results: The median serum Lp(a) concentration of 75 patients at baseline and follow-up as outpatients were 143.2 nmol/l (interquartile range (IQR) 90.9–186.0) and 141.4 nmol/l (IQR 76.2–197.0) respectively, p=0.049. Increased troponin T level at baseline was associated with ≥20% higher Lp(a) concentration at follow-up. Multivariable ordinal logistic regression analysis showed 38% increase with higher Lp(a) concentration at follow-up for a 1 unit increase in loge troponin T (OR 1.38, 95% CI [1.08–1.76]; p=0.011). Elevated baseline troponin T was associated with a ≥30% increase of Lp(a) concentration at follow up (OR 1.31 [1.01–1.70]; p=0.045). In patients with severely elevated troponin T level ≥500 ng/l at baseline, 13.6% were reclassified as having elevated Lp(a). There were six patients with an elevation of Lp(a) >50% (range 50.9–184.9%) when rechecked as an outpatient; all of them had an initial baseline elevated troponin T level of >14 ng/l. Conclusion: There is clinically significant variability of Lp(a) in patients with elevated troponin T concentration and they may have a falsely lowered Lp(a) concentration during acute admission to hospital. Patients with Lp(a) concentrations 70–120 nmol/l measured when troponin T was elevated or during acute clinical events should have their Lp(a) concentrations retested during follow-up as an outpatient.