High serum nitrates levels in non-survivor COVID-19 patients

OBJECTIVE

Higher blood nitrate and nitrite levels have been found in coronavirus disease 2019 (COVID-19) patients than in healthy subjects. The present study explores the potential association between serum nitrate levels and mortality in COVID-19 patients.

DESIGN

A prospective observation study was carried out.

SETTING

Eight Intensive Care Units (ICUs) from 6 hospitals in the Canary Islands (Spain).

PATIENTS

COVID-19 patients admitted to the ICU.

INTERVENTIONS

Determination of serum nitrate levels at ICU admission.

MAIN VARIABLE OF INTEREST

Mortality at 30 days.

RESULTS

Non-surviving (n=11) compared to surviving patients (n=42) showed higher APACHE-II (p<0.001) and SOFA scores (p=0.004), and higher serum nitrate levels (p=0.001). Logistic regression analyses showed serum nitrate levels to be associated to 30-day mortality after controlling for SOFA (OR=1.021; 95%CI=1.006-1.036; p=0.01) or APACHE-II (OR=1.023; 95%CI=1.006-1.041; p=0.01). There were no differences in the area under the curve (AUC) for mortality prediction by serum nitrate levels (AUC=83%; 95%CI=73-92%; p<0.001), APACHE II (AUC=85%; 95%CI=75-96%; p<0.001) and SOFA (AUC=78%; 95%CI=63-92%; p=0.005) based on the DeLong method. The Kaplan-Meier analysis found patients with serum nitrates levels>68.4μmol/l to have a higher mortality rate (hazard ratio=138.8; 95%CI=22.3-863.9; p<0.001).

CONCLUSIONS

The main novel finding was the association between serum nitrate levels and mortality in COVID-19 patients controlling for the SOFA or APACHE-II scores, though larger studies are needed to confirm this observation.

Rapid automated determination of adenosine deaminase and lysozyme for differentiating tuberculous and nontuberculous pleural effusions

The catalytic concentration of pleural adenosine deaminase (ADA) and the ratio of pleural lysozyme (PL) to serum lysozyme (SL) were measured in consecutive patients (49 tuberculous and 179 nontuberculous) with two automated procedures in a Hitachi 717 analyzer. Using sensitivity and specificity curves, we established cutoff values at 33 U/L for ADA and 1.7 for the PL/SL ratio. The sensitivity of ADA activities for tuberculous effusion was 90%, specificity 85%. Combining ADA with the PL/SL ratio enhanced specificity to 99%. However, high values for ADA and lysozyme ratios are not, alone or in combination, sensitive or specific enough to replace pleural biopsy or culture of pleural fluid for the diagnosis of tuberculous empyema.

Rapid automated determination of adenosine deaminase and lysozyme for differentiating tuberculous and nontuberculous pleural effusions

The catalytic concentration of pleural adenosine deaminase (ADA) and the ratio of pleural lysozyme (PL) to serum lysozyme (SL) were measured in consecutive patients (49 tuberculous and 179 nontuberculous) with two automated procedures in a Hitachi 717 analyzer. Using sensitivity and specificity curves, we established cutoff values at 33 U/L for ADA and 1.7 for the PL/SL ratio. The sensitivity of ADA activities for tuberculous effusion was 90%, specificity 85%. Combining ADA with the PL/SL ratio enhanced specificity to 99%. However, high values for ADA and lysozyme ratios are not, alone or in combination, sensitive or specific enough to replace pleural biopsy or culture of pleural fluid for the diagnosis of tuberculous empyema.