Preparation and Examination of Skin Smears

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The skin smear is a valuable, cost-effective tool in the routine management of the patient with Hansen's disease. The smear is a means of estimating the number of acid-fast bacteria present, reported as the Bacterial Index (BI), and is important in determining the type and severity of disease as well as assessing the response to treatment.

General

  • Initial skin smears are usually taken from 6 “routine sites” (both earlobes, elbows, and knees) as well as several typical lesions from the patient. Repeat smears are obtained from 3 to 4 of the most active sites previously tested to evaluate progress.
  • The time interval between repeat smears is determined by the physician, but in general, annual smears are adequate for monitoring response to treatment and during the following-up period to detect any evidence of relapse.
  • All microscopic slides on which skin smears are made should be precleaned in 70% alcohol, acetone, or alcohol-acetone to remove amorphous debris. The slides are wiped dry with a clean hand towel. Blades that are used in smear taking are likewise cleaned.
  • Slides should be air-dried and NEVER heat fixed.
  • They may be sent in protective mailers to:

National Hansen's Disease Program
Attention: Clinical Laboratory – Skin Smears
9181 Interline Avenue
Baton Rouge, LA 70809
Phone: 225-756-3733

Procedure for Obtaining Smears

  1. Universal precautions should be observed in obtaining skin smears.
  2. The skin is cleansed with 70% alcohol and air-dried or wiped dry with cotton.  (Zephiran tends to make the skin too slippery and is not recommended.)
  3. A fold of skin is made relatively avascular by pinching or mild clamping.  If the skin cannot be grasped by pinching, it can be compressed.  A surgeon's glove may aid in grasping.
  4. Local anesthesia is generally unnecessary.  (If there is not adequate decrease in sensation, obtain local anesthesia with 1% Xylocaine or Ethyl Chloride spray.) The compression of the skin by pinching aids in the anesthesia.
  5. An incision 3-5 mm long and 2-3 mm deep is made with a alcohol cleansed, single-edged razor blade.  A scalpel with a #15 Bard-Parker blade may also be used.  Mild pressure to maintain relative avascularity is continuously applied to the area until an adequate smear has been obtained.
  6. A small amount of blood does not interfere with the reading, but large amounts should be avoided and can usually be controlled by the amount of pressure of the pinch.  If excessive bleeding occurs, it can be wiped away with a cotton swab.
  7. After the incision is made, and before the blade is withdrawn, the inner surface of the wound is scraped with the blade held at a right angle to the incision.  Upon scraping, tissue fluid and dermal tissue are obtained.

  8. The material is transferred to the cleaned microscope slide.  A moderately thick smear, with a visible uniform opacity is made.  The smear is made in a circular manner on the slide, no larger than a pencil eraser (5-7 mm) , beginning peripherally and ending in the center, leaving a central “button” (2-4 mm) which can be easily focused upon with the microscope.  Slides should be properly labeled as shown below in the sample diagram for 3 routine sites.
     

    Name. 1. R knee, 2. r elbow, 3. r ear, date
  9. A Band-Aid is generally sufficient to protect the smear site.
  10. A single technician takes all smears to ensure more uniform and consistent results.
  11. The smears are then sent to the National Hansen's Disease Program for reading.
  12. A chart to diagram sites of the skin smears is linked from the top of this page.

Watch Video: Performing Routine Skin Smears

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