Which finding would most strongly suggest sample collection contamination rather than true urinary pathology?

• A. Numerous WBCs in the sediment
• B. RBC casts
• C. Many squamous epithelial cells
• D. Hyaline casts

Answer: (C)

A large number of squamous epithelial cells in urine sediment points to contamination from the distal urethra or external genitalia during collection. Squamous cells line these tissues and their abundance suggests the sample wasn’t a clean-catch or midstream specimen, so it doesn’t accurately reflect bladder urine. In contrast, numerous white blood cells indicate infection or inflammation in the urinary tract, red blood cell casts signal renal (glomerular) pathology, and hyaline casts are a common, nonspecific finding in concentrated or dehydrated urine. Thus, the presence of many squamous epithelial cells is the strongest cue that the sample is contaminated rather than representing true urinary pathology.