Fine needle aspiration biopsy (FNAB) offers a simple outpatient technique for specimen collection in paediatric tuberculosis (TB) suspects with peripheral lymphadenopathy. Culture facilities are usually centralized; to perform FNAB with mycobacterial culture on an outpatient basis requires use of a sterile transport medium to facilitate bedside inoculation, maintain organism viability and reduce contamination risk en route to the laboratory.
We compared the mycobacterial yield and time to positive culture following bedside inoculation into standard MGIT tubes versus initial inoculation into an inexpensive “in house” liquid growth medium used for transport to the laboratory followed by immediate and delayed MGIT inoculation (laboratory inoculation).
Over the period of one year 150 FNAB’s were performed; 57 (38%) cultured M. tuberculosis complex. There was one case each of NTM and M bovis BCG, with the remaining 55 being M tuberculosis. Results were concordant in 142 (94.7%) bedside and laboratory inoculation pairs. There was no significant difference in time to positive culture between the bedside and laboratory inoculation tubes (16.2 days S.D. 0.87 versus 17.1 days S.D. 0.85). There were 31 pairs with matched immediate and delayed laboratory inoculation culture results, of which 29 were concordant (93.6 %). The 2 discordant pairs showed no growth in the delayed culture; both had required repeated decontamination due to bacterial contamination introduced in the laboratory.
The use of inexpensive “in house” liquid growth medium transport bottles, combined with practical tuition in FNAB, will improve cost effective diagnosis of TB at primary health care level.
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