Diagnostic value of urinary microprotein concentration for patients with negative urinary protein test results and positive urinary casts on microscopic examination

OBJECTIVE: To analyze the association between positive urinary casts on microscopic examination and urinary microprotein concentration in the case of negative urinary protein test results. This study also investigated the diagnostic value of urinary microprotein examination. SUBJECTS: A total of 949 samples that were analyzed with a UF‐1000i Urine Analyzer and returned cast alarm results were categorized into two groups, a positive and negative group, according to qualitative urinary protein sulfosalicylic acid test results. Then, 54 samples with negative protein test results but positive cast results according to microscopic examination were selected as the study group; 60 normal people with healthy physical examination results were selected as the control group. Both groups underwent urinary microprotein tests, including urinary microalbumin (mAlb), α1‐microglobulin (A1M), transferrin (TRU), and immunoglobulin G (IgG). T tests were used to evaluate mean differences between groups and chi‐square tests were used to calculate ratio differences between groups. RESULTS: (a) Microscopic examinations of the positive and negative protein groups revealed no statistically significant difference in cast detection rate (P = .421). (b) Among the 54 samples in the study group, 37 were found to have abnormal casts, while in the remaining 17 samples, only hyaline casts were detected. (c) The detection levels of mAlb, A1M, and IgG in the study group were significantly higher than the control group (P values < .05). CONCLUSION: Urinary microprotein test should be included in the re‐examination rules for routine tests for patients with negative protein results and positive casts under microscopic examination.