A markedly alkaline urine pH is most likely due to which artifact?

A markedly alkaline urine pH is most likely due to which artifact?

• A. Radiographic contrast media
• B. Improperly preserved specimen
• C. Renal tubular acidosis
• D. High protein diet

Answer: (B)

A markedly alkaline urine pH can be an artifact from how the sample was handled. If a urine specimen is not preserved properly or is left unpreserved, bacteria in the specimen can grow and convert urea into ammonia. This ammonia raises the pH, making the urine appear more alkaline than it truly is. Refrigeration or adding a preservative slows or prevents this bacterial activity and keeps the pH closer to the patient’s real value. In contrast, true physiological or dietary causes are less likely to produce a sudden, marked alkaline shift due to preanalytic handling alone. Renal tubular acidosis can cause alkaline urine, but that reflects a kidney defect, not an artifact of specimen handling. A high-protein diet tends to acidify urine rather than alkalinize it.

A markedly alkaline urine pH can be an artifact from how the sample was handled. If a urine specimen is not preserved properly or is left unpreserved, bacteria in the specimen can grow and convert urea into ammonia. This ammonia raises the pH, making the urine appear more alkaline than it truly is. Refrigeration or adding a preservative slows or prevents this bacterial activity and keeps the pH closer to the patient’s real value.

In contrast, true physiological or dietary causes are less likely to produce a sudden, marked alkaline shift due to preanalytic handling alone. Renal tubular acidosis can cause alkaline urine, but that reflects a kidney defect, not an artifact of specimen handling. A high-protein diet tends to acidify urine rather than alkalinize it.