Recent reports suggest that cardiovascular (CV) events are associated with vascular calcification (VC) on plain radiographs. Kidney Disease Improving Global Outcomes (KDIGO) recommends that lateral abdominal radiography can be used to detect the presence or absence of VC [1]. A previous report showed that an abdominal aortic calcification (AAC) score of ≥ 7 on lateral abdominal radiography was well correlated with a coronary artery calcium score of ≥ 100 on electron beam computed tomography [2]. Another report showed that the middle to highest tertile AAC score of ≥5 was associated with an increased risk of CV events compared with the lowest tertile AAC score of < 5 in dialysis patients [3]. Recently, Kwon et al [4] showed that an AAC score of >8 predicted higher mortality and CV events in hemodialysis patients. I fully understand the authors’ opinion to determine a cut-off value of 8 based on the data of mortality. However, optimal AAC score cutoff values for CV events should be slightly lower than cutoff values for mortality because CV events frequently occur and are an important issue related to morbidity, such as intradialytic hypotension in hemodialysis patients.

The authors reported that AAC progression was found in 68% of patients with a follow-up duration of 3 years. VC on plain radiographs definitely progresses, and the progression of aortic calcification on plain radiographs is also related to an increased risk of mortality in dialysis patients. Approximately one-third of dialysis patients show VC progression on plain chest X-rays within 1–2 years compared to baseline [5]. To acquire more information regarding the harmful impact of AAC progression, I would like to suggest that the authors should precisely define AAC progression such as increases of AAC score and evaluate the risk of CV events or mortality according to AAC progression. Additionally, the authors proved that corrected serum calcium concentration was partially related to AAC progression. As the authors mentioned [4], evaluations of total calcium load and total dose of active vitamin D supplementation resolve the questions about the effect of calcium on AAC progression and help clinical practice. Nevertheless, this study supports that monitoring of VC progression by following plain radiography is a cost-effective tool for quality care of dialysis patients.

The author declares no conflict of interest.

Won Suk An

Division of Nephrology, Department of Internal Medicine, College of Medicine, Dong-A University, Busan, Korea

E-mail address: anws@dau.ac.kr (WS An)

[1] Kidney Disease: Improving Global Outcomes (KDIGO) CKD-MBD Work Group. KDIGO clinical practice guideline for the diagnosis, evaluation, prevention, and treatment of Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD). Kidney Int Suppl 113:S1–S130, 2009

[2] Bellasi A, Ferramosca E, Muntner P, Ratti C, Wildman RP, Block GA, Raggi P: Correlation of simple imaging tests and coronary artery calcium measured by computed tomography in hemodialysis patients. Kidney Int 70:1623–1628, 2006

[3] Verbeke F, Van Biesen W, Honkanen E, Wikstrom B, Jensen PB, Krzesinski JM, Rasmussen M, Vanholder R, Rensma PL, CORD Study Investigators. Prognostic value of aortic stiffness and calcification for cardiovascular events and mortality in dialysis patients: outcome of the calcification outcome in renal disease (CORD) study. Clin J Am Soc Nephrol 6:153–159, 2011

[4] Kwon HY, Lee OH, Kim MJ, Joo WC, Lee SY, Kim MJ, Song JH, Lee SW: The association between mortality and abdominal aortic calcification and relation between its progression and serum calcium concentration in chronic hemodialysis patients. Kidney Res Clin Pract 33:95–102, 2014

[5] Noordzij M, Cranenburg EM, Engelsman LF, Hermans MM, Boeschoten EW, Brandenburg VM, Bos WJ, Kooman JP, Dekker FW, Ketteler M, Schurgers LJ, Krediet RT, Korevaar JC; NECOSAD Study Group: Progression of aortic calcification is associated with disorders of mineral metabolism and mortality in chronic dialysis patients. Nephrol Dial Transplant 26:1662–1669, 2011

We appreciate your interest in our article entitled “The association between mortality and abdominal aortic calcification (AAC) and relation between its progression and serum calcium concentration in chronic hemodialysis patients” [1]. Vascular calcification, including aortic calcification, is highly prevalent in dialysis patients [2], and hyperphosphatemia should be a major stimulus for vascular calcification [3]. However, several other clinical factors such as hypercalcemia and elevated calcium x phosphate product are also known to be associated with progression of arterial calcification in dialysis patients [4].

We agree with your opinion regarding our report on the association of AAC and the mortality and its progression with serum calcium concentration [1]. What we established was the optimal AAC cutoff score for predicting mortality, not cardiovascular events. Thus, it cannot be used for predicting the cardiovascular events. What was not clearly defined in our study was the progression of AAC. This issue might have been resolved by comparing the plain radiographs of multiple sites including chest, abdomen, pelvis, hand, and lower extremities, as in another study [5].

None.

Seoung Woo Lee

Division of Nephrology and Hypertension, Department of Internal Medicine, Inha University College of Medicine, Incheon, Korea

E-mail address: swleemd@inha.ac.kr (SW Lee)

[1] Kwon HY, Lee OH, Kim MJ, Joo WC, Lee SY, Kim MJ, Song JH, Lee SW. The association between mortality and abdominal aortic calcification and relation between its progression and serum calcium concentration in chronic hemodialysis patients. Kidney Res Clin Pract 33:95–102, 2014

[2] Guérin AP, London GM, Marchais SJ, Métivier F: Arterial stiffening and vascular calcifications in end-stage renal disease. Nephrol Dial Transplant 15:1014–1021, 2000

[3] Zheng CM, Lu KC, Wu CC, Hsu YH, Lin YF: Association of serum phosphate and related factors in ESRD-related vascular calcification. Int J Nephrol 2011: doi:10.4061/2011/939613

[4] Mizobuchi M, Towler D, Slatopolsky E. Vascular calcification: The killer of patients with chronic kidney disease. J Am Soc Nephrol 20:1453–1464, 2009

[5] An WS, Son YK. Vascular calcification on plain radiographs is associated with carotid intima media thickness, malnutrition and cardiovascular events in dialysis patients: a prospective observational study. BMC Nephrology 14:27, 2013