Medicine is Not an Exact Science
Ramon F. Abarquez, Jr., MD, EFACC, FAsCC, FPCP, FPCC, CSPSH
RED cell distribution width or RDW is usually elevated in conditions of increased erythrocyte destruction or ineffective erythropoiesis and an important biomarker in a variety of acute and chronic pathological conditions, independently associated with morbidity and mortality in cardiovascular and other various diseases, including coronary artery disease, heart failure, diabetes, stroke, and venous thromboembolism.
RDW is elevated in patients with hypertension compared with those with normotension, with a non-dipper pattern compared with those with a dipper pattern, as well as in reverse dipping, which was recently regarded as an independent predictor for lacunar infarction and carotid plaque formation. (Yan B, Peng L, et al. Medicine 2015;94:e604; Eur J Neurol 2015;22:1022–5) There was significantly increased RDW in hypertensive reverse dippers (13.52±1.05) than dippers (13.25±0.85) (p=0.012).
Moreover, multinomial logistic regression analysis showed that RDW (OR 1.325, 95 percent CI 1.037 to 1.692, p=0.024) and diabetes mellitus (OR 2.286, 95 percent CI 1.380 to 3.788, p=0.001) were significantly different when comparing the reverse-dipper BP pattern with the dipper pattern.
However, there was no difference of RDW between the non-dipper pattern and the reverse-dipper pattern (OR 1.036, 95 percent CI 0.867 to 1.238, p=0.693). In addition to this, RDW was negatively correlated with the decline rate of nocturnal systolic BP (r=-0.113; p=0.003) and diastolic BP (r=-0.101; p=0.007). The study results suggested that RDW might be associated with the abnormal dipper BP patterns of either reverse dipping or non-dipping homogeneously examined with 24-h ABPM. (Su D, BMJ Open. 2016 Feb 23;6:e010456)
RDW in non-dippers
Non-dipper hypertension is associated with higher inflammation and worse prognosis. RDW and high-sensitive C-reactive protein (hsCRP) are elevated in non-dipper hypertensive patients was compared with dippers among 247 essential hypertensive patients.
Patients were divided into the two groups on the basis of the results of 24-h ABPM: 127 dipper hypertensives and 120 non-dipper hypertensives. Non-dippers had significantly higher RDW levels than dippers [14.6 (13.8-17.0) vs 13.0 (12.5-13.4), p < 0.001, respectively].
After adjustment for hemoglobin, low-density lipoprotein-cholesterol, sex, age, and hs-CRP, mean RDW values were for dipper and non-dippers 13.4 (12.4-13.2) and 14.5 (13.7-16.8), respectively (p < 0.001). RDW was negatively correlated with the percentage decline of systolic and diastolic BP from day to night (r = – 0.392, p < 0.001 and r = – 0.294, p < 0.001, respectively). Serum hsCRP levels were also significantly higher in the non-dippers (p < 0.001) and it was significantly positively correlated with RDW (r = 0.403, p < 0.001).
Optimal cut-off value of RDW to predict non-dipping pattern was > 13.8 percent, with 80 percent sensitivity and 75 percent specificity. RDW is significantly increased in patients with non-dipper hypertension compared with the dipper hypertension.
Inflammatory activity was closely related to RDW in non-dipper hypertensives. RDW, as easy and quick measurable tool, can predict non-dipping pattern in essential hypertension. (Ozcan F, Blood Press. 2013 Apr;22:80-5)
RDW in stroke
Stroke patients had significantly higher median RDW than control subjects in patients who had more severe rather than milder strokes rated with all three scoring systems (GCS, CNS, and NIHSS).
The median RDW values were significantly elevated for patients who had moderate rather than mild strokes rated by GCS and CNS and for patients who had severe rather than mild strokes rated by NIHSS (0.760 (95 percent confidence interval, 0.676-0.844).
Separation of stroke patients and control groups was optimal with RDW 14 percent (sensitivity, 71.6 percent; specificity, 67.5 percent; accuracy, 70.3 percent). In stroke patients who have symptoms <24 hours, the RDW may be useful in predicting the severity and functional outcomes of the stroke. (Kara H, Neuropsychiatr Dis Treat. 2015 Mar 18;11:733-9)
RDW in acute coronary syndrome
Overall, considerable and convincing evidence has been brought that an increased RDW value is associated with acute coronary syndrome (ACS) [including acute myocardial infarction (AMI)], ischemic cerebrovascular disease (including stroke), peripheral artery disease (PAD), as well as with atrial fibrillation (AF), heart failure (HF), and hypertension. Higher anisocytosis also significantly and independently predicts adverse outcomes in patients with these conditions.(Danese E, J Thorac Dis. 2015 Oct;7:E402-11)
RDW and microvascular disease
Decreased red blood cell deformability among patients with higher RDW values impairs blood flow through the microcirculation, resulting in the diminution of oxygen supply at the tissue level, particularly among patients suffering from myocardial infarction treated with urgent revascularization. (Bujak K, Dis Markers. 2015;2015:824624)
Vital Signs Issue 88 Vol. 4, June 1-30 2016