Ionized magnesium in serum and ultrafiltrate: pH and bicarbonate effect on measurements with the AVL 988-4 electrolyte analyzer.

Ͻ1.6 ␮g/L for cTnI. The reported reference value for cTnT was Ͻ0.1 ␮g/L [4]. To verify the URL for cTnT, cTnI and cTnT were measured in 50 patients admitted to our hospital for suspected myocardial infarc-tion. The relationship between cTnI (x) and cTnT (y) was y ϭ 0.147x Ϫ 0.144 (r ϭ 0.900). Thus, a theoretical URL of 0.09 ␮g/L for cTnT was obtained, which is same as that recommended by the manufacturer. cTnI and cTnT were measured in 15 patients (median age, 59 years; range, 24 –90 years; sex, 12 men and 3 women) with early posttraumatic rhabdomyolysis in the first 24 h after admission to the hospital. Four patients presented no detectable cTnI at admission, and the cTnT ranged from 0.01 to 0.038 ␮g/L, therefore being under the URL for cTnT. In these patients, CK was up to 480-fold above the URL. For the other patients (with increased CK from 31-to 1450-fold above the URL) with detectable cTnI at admission, a second analysis was performed 24 h later. Fig. 1 shows a close relationship (r ϭ 0.837) between cTnI and cTnT for the 14 patients (24 samples) with rhabdo-myolysis: 8 patients had both cTnI and cTnT below their respective URLs; 4 patients had both cTnI and cTnT above their respective URLs (maximal increase: 4.4-and 3.2-fold over the URL for cTnI and cTnT, respectively); and three samples from 2 patients had cTnI below the URL but cTnT above the URL (1.5-and 1.7-fold increase, respectively). In these two patients creatinine was Ͼ250 ␮mol/L. These results suggested that cTnT might be unexpectedly increased in renal failure. Although obtained with the first-generation troponin T, such a discordance between cTnI and cTnT was reported previously in renal disease [5]. However, a lower URL for cTnI (about 0.6 ␮g/L) would give nearly complete concordance between cTnI and cTnT values. The cTnI URL used in our laboratory corresponds to the value for the diagnosis of acute myo-cardial infarction, but a cutoff of 0.4 ␮g/L has been used recently to predict the risk of mortality in patients with acute coronary syndrome [6]. The last patient studied in this work had very high cTnI and cTnT values (239 and 17.7 ␮g/L, respectively), associated with a CK 277 times the URL (not shown on the figure). Thus, our results demonstrated that cTnI and second-generation troponin T showed similar changes in patients with early posttrau-matic rhabdomyolysis. We gratefully acknowledge …