High-sensitivity Cardiac Troponin I Changes Following Subcutaneous Needle Puncture, Restraint, and Venipuncture in...

Cardiac troponin I (cTnI) is a sensitive biomarker of myocardial injury in which procedure-related stress may cause mild, non-injury-related increases. This study aimed to characterize procedure-related variability of high-sensitivity cTnI and related biomarkers in cynomolgus monkeys and to compare a single molecule counting (SMC) assay with an enzyme-linked immunosorbent assay (ELISA).

Five male cynomolgus monkeys received subcutaneous physiological saline (2 ml/kg). Blood was collected under restraint at 0 (baseline), 0.5, 1, 2, 4, 8, and 24 h. cTnI was measured by SMC [lower limit of quantification (LLOQ): 0.7 pg/ml] and ELISA (LLOQ: 156 pg/ml). Cardiac troponin T, creatine kinase (CK), lactate dehydrogenase (LDH), and their isoenzymes (CK-MM, CK-MB, LDH1, LDH2, LDH4, LDH5), aspartate aminotransferase (AST), heart-type fatty acid-binding protein (H-FABP), and myoglobin were measured. Post-procedure values were compared with the baseline.

With SMC, cTnI was below the LLOQ at baseline in all animals, increased significantly at 2 and 4 h (peak at 4 h: mean approximately 16 pg/ml), and returned to near baseline by 24 h. With ELISA, baseline cTnI was below the LLOQ in four of five animals. Many post-procedure values were also below the LLOQ, although cTnI increased at 2 and 4 h (peak at 4 h). The cTnI quantification rate was higher with SMC (83%) than with ELISA (54%). cTnT, H-FABP, and myoglobin increased transiently and returned to baseline by 24 h, whereas CK and LDH and their isoenzymes and AST increased but remained above baseline at 24 h.

Subcutaneous needle puncture, restraint, and venipuncture can produce slight, transient increases in high-sensitivity cTnI. The SMC assay detected low-level variability better than ELISA, supporting stress-aware interpretation with baseline adjustment and control comparisons.