Urinary Histamine levels in patients with acute dengue
A study carried out in a small cohort of patients, who had severe dengue showed that 24-hour urine histamine was higher in patients with DHF compared to healthy individuals (Syenina A et al., 2015). Therefore, in order to understand the possible role of histamine in disease pathogenesis, we determined the urinary histamine levels in patients recruited ≤ 4 days of illness (n=91), between 5 to 6 days of illness (n=37) and 29 healthy individuals. Of the 91 patients recruited ≤ 4 days of illness, 52 had DF and 39 had DHF. In comparison to healthy individuals (median 0.22, IQR 0.07–0.76ng/mg creatinine), patients with DF (median 2.92, IQR 0.53–7.83ng/mg creatinine,) and those who proceeded to develop DHF (median 5.4, IQR 1.10-5.4ng/mg creatinine, p= ˂ 0.0001) had significantly higher levels of urinary histamine (p<0.0001) (Fig 6a) . Although patients with DHF had higher levels of urinary histamine compared to patients with DF it was not statistically significant (p=0.31) (Fig 6a) . Although the urinary histamine levels were lower during day 5 to 6 in patients with DF (median 0.15, IQR 0.06 – 0.86ng/mg creatinine, p= 0.80) compared to healthy individuals, the histamine levels of those with DHF was still high (median 0.29, IQR 0.05 – 1.12ng/mg creatinine). (Fig 6a) .
There was no significant difference in urinary histamine levels in patients with primary and secondary dengue (Fig 6b) and there was no relationship with the viral loads (Fig 6c) . The urinary histamine levels did not significantly correlate with urinary LTE4 levels in patients with DF (Spearman r = -0.08335, p = 0.56) or DHF (Spearman r = -0.2446, p= 0.13) (Fig 6d) .