ANSWERS TO LAB ERROR QUESTIONS

ANSWERS TO THE QUESTIONS ON THE LABORATORY ERROR POST

QUESTION 1:

This is a ZN stain of the sputum. What is seen on the slide?

Pink bacilli (rod shaped bacteria), these are acid fast bacilli, typical of mycobacteria. While the sputum would have to be cultured to confirm the diagnosis, it is probably Mycobacterium tuberculosis.

QUESTION 2:

From the above information, is it likely that any patients or staff in the ward were at risk of acquiring TB infection from the father? If so, give three points for action.

The father is sputum positive, that means he is infectious with TB, and could infect anyone (patients or staff) who is susceptible, and who was close to him when he was coughing.

Action points could include the following:

§         Check if any children on the ward had not had BCG. Advice from the district TB officer should be sought. This would be particularly important if any child was known to be HIV positive, or had other reason for reduced immunity

§         All staff should be told to inform the senior hospital nurse if they develop a cough or become otherwise unwell

§          

QUESTION 3:

TB is not uncommon among adults in this area, so it may be there is no link between the two cases. HOWEVER, do you have any suggestion how there may be a link between the two cases?

The possible links (but we do not know the answers yet) could be:

a). The lab aid and the cleaner were both on the children's ward at various times when the father was there, and so became infected from him,

b). There may be no link, either with the father or the hospital. Both could have been infected in the community,

c). They may both have been exposed to infection in the laboratory.

QUESTION 4:

From the findings, can you explain how and why the lab aid and the cleaner may have become infected, but not the junior technician?

(These were the findings:

• the junior laboratory technician had performed ZN staining correctly and had worn a mask while handling the specimen
• the junior technician was busy with other tasks to do, and had left the specimen on the bench, rather than discarding it or putting in the refrigerator for storage
• when the lab aid cleaned the bench the following morning, she accidently knocked the specimen pot on the floor, which cracked and the lid fell off.
• the cleaner, who was in the laboratory at the same time, helped the lab aid to clean up the sputum, and rinsed the pot under a tap)

The junior technician wore a mask while processing the specimen, and apart from not discarding the specimen correctly, appears to have followed the correct protocol.

Both the lab aid and the cleaner were exposed to infectious material when the specimen pot fell and cracked, and in the process of cleaning up.