The Detection of Hyaline Casts in Patients Without Renal Dysfunction Suggests Increased Plasma BNP

Casts in urinary sediments are useful in the identification of kidney diseases. Among them, hyaline casts have not previously been considered as pathognomonic. However, hyaline casts can occasionally be found in patients undergoing cardiovascular treatment without renal dysfunction. We evaluated the background of these patients and also investigated their levels of plasma brain natriuretic peptide (BNP).

Samples from patients who visited the Division of Cardiovascular Disease at Nihon University Hospital (2014-2018) were examined. We set extract conditions from the laboratory information system database, setting the threshold over 60 mL/min/1.73 m² for the estimated glomerular filtration rate (eGFR), and proteinuria as absent (-) or trace (±). One hundred forty-seven of 3137 (4.7%) samples showed hyaline casts (M:F=102:45, mean age 69.5±11.2 years). Samples with hyaline casts were divided into three rank groups. We compared BNP levels among each cast group and age-matched controls using Kruskal-Wallis analysis.

The median BNP levels of the controls and the three casts groups were 23.3 pg/mL in the controls, 31.1 pg/mL in group (1+), 35.5 pg/mL in group (2+), and 45.8 pg/mL in group (≥3+). The median BNP levels differed significantly between two casts groups (group (2+) and group (≥3+)) and the control group (P<0.05 and P<0.01, respectively).

Hyaline casts could be detected in patients with normal renal function. When hyaline casts are more than 2+, the physician should consider checking plasma BNP levels of the patient.