frotis

Frotis, in medical laboratory terminology, refers to a smear: a sample spread as a thin film on a glass slide to permit microscopic examination. Smears are used across hematology, microbiology, and cytology to assess cellular morphology, staining characteristics, and the presence of microorganisms or abnormal cells. The technique is valued for being relatively rapid, inexpensive, and suitable for screening large numbers of specimens.

Preparation typically involves collecting a specimen (for example, a drop of peripheral blood from a finger or vein, body fluids, tissue aspirates, or sputum), spreading it on a slide to create a monolayer, fixing the smear (air-drying or chemical fixation), and staining with appropriate dyes (for example, Wright or Giemsa for blood smears; Papanicolaou for cytology; Ziehl-Neelsen or Gram staining for bacteria). The resulting stained slide is examined under a light microscope, often at multiple magnifications.

Common types include peripheral blood smear, which assesses red and white cell morphology, platelet clumping, and can reveal anemia or leukemias; cytology smears such as Pap smears for cervical cancer screening; sputum or bronchoalveolar lavage smears for infectious agents; and fine-needle aspiration smears used to evaluate lesions.

Interpreting frotis requires skilled microscopy and standardized staining to minimize artifacts. Limitations include sampling bias, staining variability, and the potential for artifacts that mimic pathology. Smear findings are typically integrated with clinical information and additional tests for a final diagnosis.