Measurement of albuminuria during acute myocardial infarction and its relation with prognosis

Giuseppe Berton

Conegliano General Hospital
Department of Cardiology
Conegliano
Italy
Tel: +39 0438 663613
Fax: +39 0438 663360
E-mail address: giube.s{at}aliceposta.it

Paolo Palatini

Clinica Medica IV
University of Padova
Padova
Italy

In the recently published study by Kragelund et al.,1 fasting insulin, blood glucose, HbA1c, and microalbuminuria were measured in a large sample of non-diabetic patients with acute myocardial infarction (AMI) between the second and the fifth day after admission. All the above markers were associated with global mortality after 7 years of follow up at univariable analyses, but only insulin level remained an independent predictor of outcome at multivariable analysis. We believe that the predictive power of albumin excretion (AE) has been overlooked by the authors owing to a series of methodological problems. First, the authors measured AE on the first voided morning urine sample and expressed it as a concentration. This is not an accurate method for assessing urinary albumin, because to obtain a reliable estimate of AE, independent of urine flow rate, AE should be corrected for urinary creatinine.2 Several studies have shown that measurement of AE rate (in overnight or 24 h samples) is more closely associated to the ‘real’ albumin escape than AE.2,3 Secondly, the authors collected the urine samples ‘at day 2–5 after admission’. This 4 day range in sampling AE weakened the predictive power of AE for outcome, because AE during AMI peaks at the first day and has a rapid decline throughout the first week after AMI. We showed that albumin to creatinine ratio in non-diabetic patients declined from 91.6±13.7 on the first day to 36.5±6.7 on the third day, and to 24.5±4.5 mg/g on the seventh day after admission for AMI.4 A similar trend was observed by Gosling et al.5 This indicates that AE values decrease by a ratio of 2.5 and 3.7 on the third and seventh day, respectively. Therefore, in all patients AE assessment should be performed on the same day after AMI. There is another point of the article by Krakenburg et al.1 that deserves a comment. The authors hypothesized that the independent association between AE and mortality previously found by our group may be due to the presence of diabetic patients in the sample.6,7 However, the results of our recent analysis indicates that this is not the case.4 We demonstrated that the predictive power of AE in the non-diabetic segment of our population was equal to or even greater than that in the diabetic patients.4 Thus, the discrepancy between our results and those of Krakenburg et al.1 is likely to be due to the aforementioned methodological problems.

In conclusion, the non-independent prognostic power of AE reported by Kragelund et al.1 in their study is likely to be due to the inadequate assessment of urinary AE. According to our results, the best timing for urine collection in AMI patients should be set on the third day after admission.

References

  1. Kragelund C, Snorgaard O, Kober L, Bengtsson B, Ottesen M, Hojberg S, Olesen C, Kjaergaard JJ, Carlsen J, Torp-Petersen C; TRACE Study Group. Hyperinsulinaemia is associated with increased long-term mortality following acute myocardial infarction in non-diabetic patients. Eur Heart J 2004;25:1891–1897.[Abstract/Free Full Text]
  2. Rowe DJ, Dawnay A, Watts GF. Microalbuminuria in diabetes mellitus: review and recommendations for the measurement of albumin in urine. (Review). Ann Clin Biochem 1990;27:297–312.[ISI][Medline]
  3. Wiegmann TB, Chonko AM, Barnard MJ, MacDougall ML, Folscroft J, Stephenson J, Kyner JL, Moore WV. Comparison of albumin excretion rate obtained with different times of collection. Diabetes Care 1990;13:864–871.[Abstract]
  4. Berton G, Cordiano R, Palmieri R, De Toni R, Guarnieri GL, Palatini P. Albumin excretion in diabetic patients in the setting of acute myocardial infarction: association with 3-year mortality. Diabetologia 2004;47:1511–1518.[CrossRef][ISI][Medline]
  5. Gosling P, Hughes EA, Reynolds TM, Fox JP. Microalbuminuria is an early response following acute myocardial infarction. Eur Heart J 1991;12:508–513.[Abstract]
  6. Berton G, Citro T, Palmieri R, Petucco S, De Toni R, Palatini P. Albumin excretion rate increases during acute myocardial infarction and strongly predicts early mortality. Circulation 1997;96:3338–3345.[Abstract/Free Full Text]
  7. Berton G, Cordiano R, Palmieri R, Cucchini F, De Toni R, Palatini P. Microalbuminuria during acute myocardial infarction; a strong predictor for 1-year mortality. Eur Heart J 2001;22:1466–1475.[Abstract/Free Full Text]




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