How does an Aptima (Automated Processing and Testing of Infectious Materials using Amplification) swab detect yeast?

How Aptima Swab Detects Yeast in Vaginal Specimens

The Aptima swab does not directly detect yeast but rather is designed primarily for bacterial and viral pathogen detection using nucleic acid amplification test (NAAT) technology. While Aptima assays are highly sensitive for their intended targets like bacterial vaginosis pathogens and Trichomonas vaginalis, they are not specifically designed to detect Candida species.

Aptima Technology Overview

• Aptima uses transcription-mediated amplification (TMA) technology, which targets specific RNA sequences of intended pathogens rather than fungal elements 1, 2
• The system is designed to detect bacterial vaginosis-associated organisms (Gardnerella vaginalis, Atopobium vaginae) and certain sexually transmitted infections, not fungal pathogens like Candida species 3, 4

Yeast Detection Methods in Clinical Practice

• For yeast detection, conventional methods remain the standard approach:

  • Direct microscopy of vaginal secretions to visualize yeast cells and pseudohyphae 5
  • Culture on fungal selective media for species identification 5
  • Commercial biochemical tests for yeast identification 5

• For Candida vaginitis specifically, the following are recommended:

  • Examination of vaginal secretions spread directly onto microscopy slides 5
  • Semi-quantitative culture techniques using fungal selective agar 5
  • Species identification for recurrent/complicated cases 5

Specialized Candida Detection Tests

• The Affirm VP III Assay is specifically designed to detect Candida albicans (but not other Candida species) along with bacterial vaginosis and Trichomonas 5
• MALDI-TOF mass spectrometry is strongly recommended for species-level identification of cultured Candida isolates 5
• Molecular identification through sequencing is recommended when identification cannot be obtained by other methods 5

Clinical Implications

• When yeast infection is suspected, clinicians should not rely on Aptima swabs alone but should order appropriate fungal testing 5
• For vaginal candidiasis diagnosis, a combination of clinical assessment, microscopy, and culture remains the standard approach 5
• Species identification and susceptibility testing are indicated in recurrent/complicated cases and in patients with prior azole exposure 5

Common Pitfalls

• Relying solely on molecular tests like Aptima for yeast detection may lead to missed diagnoses of Candida infections 5
• Not all Candida species form filaments during infection (e.g., C. glabrata), so microscopy in such cases will show only yeast cells 5
• PCR-based procedures for Candida detection lack standardization and external validation 6
• Samples for fungal culture should not be placed in histopathology fixatives and must be kept moist 5