Final answer:
A positive leukocyte esterase test result in a urinalysis is indicative of the presence of white blood cells in the urine, which suggests an active infection, indicating that the client might have a continuing infection after treatment for pyelonephritis.
Step-by-step explanation:
The urinalysis value that should indicate to the nurse that the client has a continuing infection after a course of ciprofloxacin for pyelonephritis is Positive leukocyte esterase (C).
Leukocyte esterase is an enzyme that is typically present in white blood cells (leukocytes). A positive leukocyte esterase test in a urinalysis suggests that there are white blood cells in the urine, which typically indicates an active infection. Other options provided do not specifically indicate an ongoing infection as effectively as the presence of leukocyte esterase. For instance, a negative nitrite test (A) doesn't necessarily confirm the absence of an infection since not all bacteria convert nitrate to nitrite. A small number of red blood cells (B) could be due to a range of reasons and not directly indicative of an infection. Lastly, an amber-colored urine (D) is commonly seen and can be influenced by factors such as food intake, hydration level, and medications, but it does not directly suggest an active infection.