Small increases in troponin levels can help stratify between high and low mortality risk regardless of age, UK research shows.
A study of more than 250,000 adults undergoing troponin levels on presentation to or during an admission at one of five acute care centres found overall a positive troponin level (above the upper limit of normal) was associated with a 3.2-fold higher mortality.
The effect was particularly strong for young adults (18-20 years) who had a 10.6-fold mortality then decreased progressively with age to a mortality hazard ratio of 1.5 in patients over 90 years of age.
The study authors, writing in the BMJ, said a raised troponin level was an important clinical signal that should not be dismissed lightly regardless of age.
“Because of the high baseline risk in older patients, the absolute increment in three year mortality associated with a positive troponin result was remarkably consistent across all ages, at about 15 percentage points.”
“This consistency is because the decline in hazard ratio with age is accompanied not by waning importance of troponin levels but by rising background mortality with age in people with troponin negative results.”
Most of the increased mortality with a positive troponin test occurred in the first three months, suggesting a conservative wait and see management approach may not be appropriate.
They also found mortality increased progressively with higher troponin levels up to about >5-10×ULN but above this there was an unexpected progressive decline.
A sub-group analysis showed this relationship remained in patients with ACS but was not seen in other patients.
“Patients with the very highest troponin levels had mortality comparable to those with normal troponin levels after the first month of follow-up,” the authors said.
“Possibly the paradoxical decline in mortality at very high troponin levels in patients with ACS may be due in part to a changing case mix as troponin levels increase. In addition, a higher proportion of patients with the highest troponin levels undergoes invasive management.”
Overall, about two thirds of patients with ACS (67.7%) had angiography within the first three months but this varied with troponin levels – starting at 39.4% for troponin levels <1×ULN, 54.3% for 1 – 10×ULN and progressing steadily upwards to 90% for troponin levels >1000×ULN.
The study concluded that troponin can risk stratify between high and low mortality risk for all age groups.
“Although even weakly raised troponin levels had marked prognostic significance, clinical decisions should depend on the underlying disease and not simply on the degree of increase in troponin.”