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COLLECTING OF SAMPLES FROM FOR SKIN LESIONS

For most dermatological conditions, diagnosis may be established on the basis of physical examination and clinical history without the collection of diagnostic specimens. Important characteristics to be noted on physical examination include the nature of the skin lesions (erythematous, macular, papular, maculopapular, vesicular, bullous, petechial, purpuric, etc.) and the anatomic distribution of spread (central, peripheral, diffuse, etc.)

In cases of indeterminate diagnoses, unusual presentations, and some rare conditions, collection of specimens from rashes and/or skin lesions may be necessary. In the case of vesicular rashes, specimens for microscopy and culture are taken directly from vesicles. In other exanthemata(macular and/or papular), the diagnosis may be more readily established from alternative specimens (e.g. blood cultures, serology).

In suspected cutaneous anthrax or bubonic plague, specimens from the skin lesions (scars and buboes, respectively) and blood cultures may be taken.


MATERIALS

SUPPLIES REAGENTS

Sterile swabs and appropriate transport media

Sterile screw cap vials

Sterile lancets or needles (for piercing of vesicles).

Syringe with wide-bore needle (for aspiration of abscesses/buboes)

Wide mouth screw-cap containers (for biopsy specimens)

Glass slides and slide boxes

Sterile saline


PROCEDURE

I. Vesicular or vesiculo-pustular rash and Slide preparation (for diagnosis of viral infections).

STEP ACTION
1

HSV-infected cells are present in greatest numbers in the base of the vesicles or ulcers that are useful for direct HSV-1 and HSV-2 antigen detection.

2

Clean the fresh mature vesicle or ulcer with 70% ethanol.

3

Using a tuberculin syringe fitted with 26-27 gauge needle, insert the needle, bevel edge up, into the base of the vesicle.

4

Aspirate fluid and immediately, carefully inject the fluid into a vial containing 1- 2ml viral transport media; rinse once.

5

Lift the membrane of the vesicle and using a sterile Dacron swab, firmly rub at the base of the ulcer (Calcium alginate swabs cannot be used).

6

Immediately place the swab in the vial containing viral transport media.

7

Carefully scrape cells from base of the ulcer with scalpel or curette.

8

Rinse the lesion with two to three drops of viral transport media to make a cell suspension.

9

Aspirate the suspension and prepare three spots on a clean glass microscope slide

10

The slide should be left to dry in air.

11

Fix in cold acetone

12

Place in a slide box for transport to the laboratory


II. Crusting stage

STEP ACTION
1

Gently ease off crust with a lancet or scalpel and a pair of disposable forceps

2

Take 5-10 crusts, place them in a plastic screw-cap vial. Make sure the lid is tightly closed.

3

Label the specimen containers

4

Discard forceps, lancets and scalpels into sharps disposal container.

Do not re-use forceps on specimens from another patient.


If cutaneous anthrax is suspected, the vesicular fluid under the scar is a better diagnostic specimen than a piece of the scar.


III. Aspiration of abscesses

Aspiration of abscesses should only be performed by experienced personnel

STEP ACTION
1

Disinfect the skin overlying the abscess/bubo with 70% isopropyl alcohol.

2

Aspirate the fluid from the abscess with a sterile needle and syringe. Only enough fluid to perform the diagnostic tests is required.

3

Transfer the aspirate aseptically into a sterile tube with transport medium.

4

Gently ease off crust with a lancet or scalpel and a pair of disposable forceps



IV.  Skin biopsy

Skin biopsies from live patients are generally not appropriate specimens for field outbreak investigations. For details of the collection of skin biopsies after death for suspected viral haemorrhagic fevers, see the relevant section in Annex 9, Post-mortem specimen collection.



HANDLING AND TRANSPORT

  • Specimens for bacteriological analysis should be transported in Stuart’s or Amies medium. Swabs for suspected viral pathogens should be transported in virus transport medium. Other specimens should be handled as described in the relevant section.

  • If processing takes longer than 2 hours, bacteriology specimens can be maintained at ambient temperature for 24 hours. Specimens for virus isolation may be refrigerated at 4-8oC, and transported to the laboratory as rapidly as possible. In some instances, the outbreak investigation team may bring liquid nitrogen for specimen preservation. If this is the case, follow the instructions of the experienced laboratorian as to appropriate use.

  • If there are any questions regarding handling and transport, check with the laboratory which will be receiving the specimens. In any outbreak investigation, it should be considered essential to consult the receiving laboratory about the handling of most specimen types before setting out into the field.



COLLECTION OF URINE SAMPLES


MATERIALS

SUPPLIES REAGENTS

Sterile plastic cup with lid (50ml or more)

Clean, screw-top specimen transport containers (“universal” containers are often used)

Gauze pads

Soap and clean water (or normal saline) if possible



PROCEDURE

Collection of Mid-Stream Urine (MSU) Sample

STEP ACTION
1

Give the patient clear instructions to pass urine for a few seconds, and then hold the cup in the urine stream for a few seconds to catch a mid-stream sample. This should decrease the risk of contamination from organisms living in the urethra

2

To decrease the risk of contamination from skin organisms, the patient should be directed to avoid touching the inside rim of the plastic cup with the skin of the hands, legs or external genitalia.

Tighten the cap firmly when finished.

3

For hospitalized or debilitated patients, it may be necessary to wash the external genitalia with soapy water to reduce the risk of contamination. If soap and clean water are not available, the area may be rinsed with normal saline.

Dry the area thoroughly with gauze pads before collecting the urine.

4

Urine collection bags may be necessary for infants. If used, transfer urine from the urine bag to specimen containers as soon as possible to prevent contamination with skin bacteria. Use a disposable transfer pipette to transfer the urine.

5

Label the specimen containers



Processing Urine for Viral Isolation

STEP ACTION
1

Centrifuge the specimen at 1,500 rpm for 5 min.

2

Re-suspend the sediment in 0.5 to 2ml of viral transport media

3

Label the vial with patient’s name type of specimen and date of collection.

4

Refrigerate at 4-8oC and send as soon as possible to CARPHA or store at -70oC if shipping is delayed.



HANDLING AND TRANSPORT

  • Transport to the laboratory within 2-3 hours of collection. If this is not possible, do not freeze but keep the specimen refrigerated at 4-8oC.

  • Keeping the specimen refrigerated will decrease the risk of overgrowth of contaminating organisms

  • Ensure that transport containers are leak-proof and tightly sealed.

Caribbean Public Health Agency © 2014