Blood in Vaginal Specimens for Yeast and BV Testing
Yes, you can send vaginal specimens containing blood for both yeast and bacterial vaginosis testing, as blood does not invalidate these diagnostic tests. The presence of blood does not interfere with the key diagnostic methods used for these infections.
Why Blood Does Not Interfere
For Bacterial Vaginosis Testing
Gram stain (Nugent criteria) remains the gold standard and is unaffected by blood, as the scoring system evaluates bacterial morphotypes (Lactobacillus vs. mixed flora) which are still visible despite blood contamination 1, 2.
Amsel criteria can still be applied even with blood present, as three of the four diagnostic findings remain assessable: vaginal pH >4.5, positive whiff test (amine odor), and clue cells on microscopy 1, 2.
Molecular NAAT testing for BV-associated organisms (such as Gardnerella vaginalis and other microbiome markers) is not affected by blood, as these tests detect bacterial DNA regardless of blood presence 1, 3.
For Yeast Testing
Microscopic examination with 10% KOH preparation to visualize pseudohyphae and budding yeast remains effective, as the KOH dissolves cellular debris (including blood cells) while preserving fungal elements 4, 1.
Culture on selective fungal media is unaffected by blood contamination, as the selective media suppress bacterial overgrowth and allow Candida species to grow 4.
Vaginal pH measurement (typically <4.5 for yeast infections) can still be performed, though blood may slightly elevate pH, so interpret in clinical context 1, 3.
Practical Specimen Handling Considerations
For wet mount microscopy, examine the specimen within 30 minutes to 2 hours regardless of blood presence, as this time constraint is due to loss of Trichomonas motility, not blood interference 1, 3.
For Gram stain, place the swab directly into transport tube; specimens remain stable at room temperature for 12 hours 2, 3.
For NAAT testing, specimens in laboratory-provided transport devices (liquid Amies) remain stable at room temperature for up to 7 days, unaffected by blood 3.
Critical Caveats
Avoid contaminating the specimen with cervical mucus, as this affects test accuracy more than blood does 1.
Blood may make clue cell identification slightly more challenging on wet mount, but experienced microscopists can still recognize them, and Gram stain remains highly reliable 1, 2.
If menstrual blood is heavy, consider repeating collection after menses for optimal specimen quality, though testing can still proceed if clinically urgent 5.
Do not delay testing solely due to blood presence, as untreated vaginal infections can worsen and blood does not preclude accurate diagnosis 1, 2.