From the Guidelines
The next step in the workup of a patient with 1+ blood on urinalysis but negative RBCs on microscopy is to repeat the urinalysis to confirm the presence of hematuria, as a single positive dipstick reading without microscopic confirmation does not define microhematuria 1. This approach is based on the American Urological Association (AUA) guidelines, which emphasize the importance of microscopic examination to confirm the diagnosis of microhematuria. According to the AUA guidelines, a positive dipstick test should be followed by microscopic examination to confirm or refute the diagnosis of microhematuria, and if the microscopic examination is negative, the patient should have three additional repeat tests to confirm the presence of hematuria 1. If at least one of the repeat tests is positive on microscopy, then a work-up should be undertaken, which may include cystoscopy and upper tract imaging, depending on the patient's risk factors and symptoms 1. It is also important to consider other potential causes of a positive dipstick test, such as myoglobinuria or hemoglobinuria, and to evaluate for these conditions if suspected. However, based on the most recent and highest quality evidence, repeating the urinalysis to confirm the presence of hematuria is the most appropriate next step in the workup of a patient with 1+ blood on urinalysis but negative RBCs on microscopy. Some key points to consider in the workup of microhematuria include:
- The definition of microhematuria as three or more red blood cells per high power field on microscopic evaluation of a single specimen 1
- The importance of considering patient risk factors, such as age, sex, and smoking history, in determining the need for further evaluation 1
- The role of cystoscopy and upper tract imaging in the evaluation of microhematuria, particularly in patients with risk factors or symptoms suggestive of malignancy 1.
From the Research
Next Steps in Workup
The presence of 1+ blood on urinalysis but negative RBC on microscopy requires further evaluation to determine the cause of the hematuria.
- The initial step is to repeat the urinalysis to rule out a false-positive result 2.
- If the result is still positive, additional tests such as a complete blood count, blood urea nitrogen, and creatinine levels may be ordered to assess kidney function 2.
- Imaging studies like ultrasound or CT scan may also be considered to evaluate the kidneys and urinary tract for any abnormalities 2.
- It is essential to consider the patient's medical history, physical examination, and other elements of the urinalysis to differentiate between glomerular, renal, and urologic causes of microhematuria 2.