Accurate measurement of coronary artery calcium in cancer patients using the CT component of PET/CT scans.

OBJECTIVE: The aim of this study is to establish the correlation between a CAC score derived from the CT component of PET/CT scan (CAC-PET) using in-house software as compared to the conventional technique (CAC-Standard). In addition, the incidence of high CAC scores in asymptomatic cancer patients with low-to-intermediate cardiovascular risk will be determined. METHODS: 100 patients referred for oncologic PET/CT were prospectively recruited to have a conventional CAC score after their PET/CT. Patients with a history of cardiac disease were excluded. The nongated CT images from the PET/CT (CAC-PET) were analysed using validated in-house software with the results compared to those from gated CT analysed using the standard technique (CAC-Standard). RESULTS: The correlation of CAC scores between the two scan types was moderate [slope, 0.95; R2 = 0.91; limits of agreement (LOA) = 0.29-5.65]. Using a conventional categorical analysis, there was complete agreement in 73% of patients with one category difference in the remainder. [interclass correlation (ICC) = 0.90; Cohen's kappa = 0.63]. In total 28% of these asymptomatic low-to-intermediate-risk cancer patients had CAC scores over 300. CONCLUSION: Estimation of CAC from the CT component of PET/CT scans is a reliable method for the detection of significant CAC in cancer patients and correlates well with the standard method. This technique should permit the calculation of cardiovascular risk in cancer patients undergoing PET/CT without any additional radiation exposure. A significant number of asymptomatic low-to-intermediate-risk cancer patients were found to have a high risk of cardiovascular disease.

Inaccuracies in estimated glomerular filtration rate in one Australian renal centre.

BACKGROUND: Early identification of true renal disease (glomerular filtration rate (GFR) < 60 mL/min) results in better patient outcomes. There is now routine reporting in Australia of estimated GFR (eGFR) in all patients over age 18 who have serum creatinine measured, calculated by the Modification of Diet in Renal Disease (MDRD) formula, which was validated in an American Caucasian cohort. Significant clinical decisions and prognosis are often made on the basis of this calculation. AIM: To assess the accuracy of three estimates of GFR in an Australian population by comparing eGFR obtained by the abbreviated MDRD (aMDRD), Cockcroft-Gault corrected for body surface area (BSA) (CG) and Chronic Kidney Disease Epidemiology (CKD-Epi) formulae with a gold standard, isotopic (51) Cr-ethylenediaminetetra-acetic acid ((51) Cr-EDTA) GFR. METHODS: Patients referred with an eGFR of <60 mL/min reported by the aMDRD formula underwent isotopic measurement of GFR (over 4 h) and had eGFR calculated using CG corrected for BSA, aMDRD and CKD-Epi formulae. Data were analysed using Bland-Altman plots and regression analysis to compare methods; bias, precision and the proportion of patients correctly stratified by stage of chronic kidney disease (CKD) were also compared according to the three estimates of GFR, using (51) Cr-EDTA GFR as the gold standard. RESULTS: A total of 139 patients were recruited (female 45%), mean age 64 years and mean serum creatinine 212 µmol/L. The mean GFR (SD) (mL/min per m(2) ) for isotopic, CG, aMDRD and CKD-Epi were 47 (28), 37 (20), 32 (17) and 33 (18) (P = 0.001). CG (57%) was more likely to correctly stage CKD than aMDRD (37%) or CKD-Epi (37%), and absolute bias was significantly lower using CG than either other method (P = 0.001). CONCLUSION: In this small Australian population the CG formula corrected for BSA agreed more closely with isotopic GFR and correctly staged patients with CKD more often than the aMDRD or CKD-Epi formulae. It is important that each renal Unit considers the accuracy of estimates of GFR according to their population demographics.