Proper Procedure for Sending AFB Ear Sample for Leprosy Patient
For leprosy diagnosis, obtain slit-skin smears from both ear lobules (along with other sites), place the specimen in a sterile container, and transport to the laboratory at room temperature within 2 hours for AFB staining and culture. 1
Specimen Collection Sites
Both ear lobules should be included as primary collection sites for slit-skin smears in leprosy patients, as they yield significantly higher bacterial index (BI) and morphological index (MI) values compared to other anatomical sites in untreated patients 2
Collect specimens from multiple sites including both ear lobules, right elbow, dorsal aspect of middle phalanx of the left finger, and dorsum of middle phalanx of the right foot to maximize detection sensitivity 2
In treated patients, ear lobules may not always be the highest-yield site—bacilli can be detected at other locations when ear lobes are negative, so multiple site sampling remains important 2
Collection Technique
Use the slit-skin smear technique to obtain specimens from the ear lobules and other designated sites 2
If tissue biopsy is obtained instead of smears, prepare two suspensions: one by mincing and grinding tissue in phosphate-buffered saline (SI), and another after treating with NaOH solution and digesting with trypsin (SII), as this increases detection rates significantly 3
Transport Requirements
Place specimens in a sterile container and transport at room temperature within 2 hours for optimal results 1
For longer transport times (2-24 hours), specimens can be maintained at 4°C, though immediate transport is preferred 1
Swabs are a second-choice collection method and should only be used for superficial mycobacterial infections; tissue or aspirate specimens are preferred 1
Laboratory Processing
Request both AFB smear microscopy using Ziehl-Neelsen (ZN) stain or Fite stain and mycobacterial culture 1, 4
The Fite stain is particularly important for leprosy as it can reveal acid-fast bacilli within Schwann cells of peripheral nerves, which is pathognomonic for the disease 4
Consider requesting RLEP-PCR molecular testing in addition to microscopy, as it has significantly higher sensitivity (66.25%) compared to AFB microscopy alone (22.5%) in detecting leprosy cases, particularly in paucibacillary patients 5
Critical Considerations
AFB microscopy has low sensitivity for leprosy diagnosis—most cases remain undetected with microscopy alone, making molecular testing increasingly important in the post-elimination era 5
In skin biopsies, direct observation with ZN stain detects bacilli in only a small percentage of cases (3 out of 22 in one study), but processing tissue suspensions increases detection to 18 out of 22 cases 3
For aged or potentially nonviable bacilli, pyridine extractability of acid-fastness may occur, which can complicate interpretation but is not definitive for species identification 6
Notify the laboratory that leprosy is suspected so appropriate staining methods (Fite stain) and extended culture protocols can be implemented 1