From the Guidelines
A bad urine sample can be identified through several key indicators, including the presence of more than 10 WBCs and a significant number of epithelial cells, which must be considered contaminated, as stated in the study by 1. To determine if a urine sample is bad, several factors should be considered:
- Appearance: cloudy, unusually dark, or containing visible particles may indicate contamination.
- Temperature: should be between 90-100°F when freshly collected; samples outside this range may be tampered with or not fresh.
- Odor: unusual odor beyond the typical ammonia smell can suggest bacterial growth or contamination.
- Laboratory analysis: abnormal pH levels (normal is 4.5-8), presence of contaminants like soap or bleach, abnormal specific gravity (normal is 1.002-1.030), or lack of expected compounds like creatinine.
- Timing: samples should be analyzed within two hours of collection or refrigerated.
- Collection errors: improper mid-stream technique, contamination with menstrual blood or fecal matter, or using unclean containers can all compromise sample integrity. According to the study by 1, the method of collecting, storing, and preserving urine specimens has a critical influence on culture results, and poorly collected or preserved specimens can become easily contaminated. The study by 1 and 1 also emphasizes the importance of proper collection technique, including the use of mid-stream or clean-catch specimens, and the need for careful handling and processing of urine samples to prevent contamination. In summary, a bad urine sample can be identified by considering these key indicators and ensuring proper collection and handling techniques, as supported by the studies by 1, 1, 1, and 1. Some key points to consider when evaluating a urine sample include:
- The presence of more than 10 WBCs and a significant number of epithelial cells, which indicates contamination, as stated in the study by 1.
- The use of mid-stream or clean-catch specimens, which can help minimize contamination, as recommended in the studies by 1 and 1.
- The importance of proper handling and processing of urine samples, including analysis within two hours of collection or refrigeration, as emphasized in the study by 1.
From the Research
Identifying a Bad Urine Sample
To identify if a urine sample is bad, several factors can be considered:
- Bacterial contamination: A bad urine sample may contain a high level of bacterial contamination, which can be indicated by the presence of colony-forming units (CFU) per ml 2.
- Urine collection technique: The technique used to collect the urine sample can affect its quality. For example, holding the labia apart during sampling can reduce bacterial contamination in women 2.
- Contamination rates: Studies have shown that contamination rates can vary depending on the collection method and materials used. For example, one study found that the use of a funnel urine-collection system and silver-impregnated wipe did not reduce urine-culture contamination in adult midstream clean-catch urine cultures 3.
- Urinalysis results: A bad urine sample may produce abnormal urinalysis results, such as:
- Cloudy urine, which can be caused by precipitated phosphate crystals or pyuria 4
- Strong odor, which can be caused by a concentrated specimen or urinary tract infection 4
- False-positive or false-negative dipstick urinalysis results 4
- Abnormal specific gravity, which can indicate hydration status 4, 5
- Microhematuria, which can have a range of causes 4
- Proteinuria, which can be transient or persistent 4, 5
- Comparison with catheterization: In some cases, a bad urine sample may be compared with a sample obtained through catheterization to determine its accuracy. One study found that midstream clean-catch urine sampling produced similar results to catheterization in ambulatory women with symptoms of urinary tract infection 6.