Cancer Diagnosis Program | Biorepositories and Biospecimen Research Branch

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Boric acid converts urine into an effective bacteriostatic transport medium.

Author(s): Lum KT, Meers PD

Publication: J Infect, 1989, Vol. 18, Page 51-8

PubMed ID: 2915130 PubMed Review Paper? No

Purpose of Paper

Conclusion of Paper

Studies

1. Study Purpose

   This study investigated the effects of preserving urine with boric acid before storage at room temperature for up to 48 h on culture results and the incidence of pyuria. A fixed volume of mid-stream urine from 175 patients was poured into two sterile bottles, one of which contained boric acid such that the concentration was 20 g/L boric acid. Patients were selected based on a request for urinalysis and ample specimen volume. Specimens were then transferred to the laboratory by porter (mean 147 min, 10-960 min), allowed to settle for 15 min, and then investigated by microscopy.  More than five white blood cells/0.16 mm³ was considered pyuria. Specimens were stored at room temperature and cultured after 0, 4, 24, and 48 h. Cultures with <1 cfu/µL were classified as no growth, those with <10 cfu/µL were classified as no significant growth, those with 10-<100 cfu/µL of one organism were classified as doubtful significant growth, and those with ≥100 cfu/µL of one organism were classified as significant growth. Mixed growth was classified as type 1 if specimens cultured 10-100 cfu/µL of two or more organisms and type II if >100 cfu/µL of three or more organisms. 

   Summary of Findings:

   When cultured immediately after arrival in the laboratory, 38 unpreserved and 29 borate-preserved specimens had significant growth (≥100 cfu/µL) of a single organism, 119 borate-preserved and 113 unpreserved specimens had no growth or non-significant growth, and 27 borate-preserved and 24 unpreserved specimens had equivocal results (growth of doubtful significance or mixed growth). As room temperature storage increased, the number of unpreserved specimens considered to have significant growth increased (38 at 0 h, 42 at 4 h, 90 at 24 h, and 109 at 48 h), but in boric acid-preserved specimens the number only increased slightly (29 at 0 h, 30 at 4 h, 32 at 24 h, and 37 at 48 h). Similarly, the number of specimens negative for growth decreased in unpreserved specimens from 82 at 0 h to only 20 when stored for 48 h, but only declined from 89 to 84 in borate-preserved specimens after 48 h. Pyuria was more common in specimens that were culture positive than those that were negative in unpreserved (82% versus 19%) and borate- preserved (83% versus 20%) specimens. Importantly, the addition of boric acid may slightly increase WBC survival as after 48 h the number of specimens with pyuria in borate-preserved specimens had only decreased from 62 to 53 while in unpreserved specimens it decreased from 60 to 46.

   Biospecimens

   • Bodily Fluid - Urine

   Preservative Types

   • Other Preservative
   • None (Fresh)

   Diagnoses:

   • Other diagnoses
   • Not specified

   Platform:

   Analyte	Technology Platform
   Cell count/volume	Microbiological assay
   Cell count/volume	Light microscopy

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Storage	Time at room temperature	0 h 4 h 24 h 48 h
   Biospecimen Preservation	Type of fixation/preservation	Boric acid None (fresh)

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