Leprosy mailing list – June 1st,
2006
Ref.: Laboratory
diagnosis of leprosy
From: Clapasson A., Genoa,
Italy
Ccn: all.
Dear
Salvatore,
I wish to thank Dr Fernandez from Santo Domingo (LML May
31st, 2006) for introducing this important subject.
Lepromin
contains killed Mycobacterium leprae and there are different
types. PPD or purified protein derivative of Mycobacterium bovis
is made by purification with ammonium sulphate.
Different
laboratory tests are available for diagnosis of leprosy. Hystochemical or cytological
stainings (Fite Faraco o Ziehl Neelsen) have low sensibility, you can
see one BAR out of three. Low
sensibility also applies to serology tests.
The PCR is
able to amplify million times the single target, but it needs:
- an
efficient method of extraction of DNA (in the biopsy of a PB
patient there are a lot of tissue inhibitors and so your Taq
polymerase cannot work);
- a target
for the primers otherwise the Taq polymerase cannot work;
- the target
must be intact otherwise the Taq polymerase cannot work;
If the RLEP
sequences are used it can be characterized less than a bacterium but,
there are other negative factors that should be taken into account:
extraction, target, and the more important thing that is
“integrity” of the target.
If one
calculates the cost of the primers and of the other reagents the
“homemade kit” is less expensive than ones that are on the market.
Conclusion:
only the careful comparison of clinical and laboratory findings can
give reliable results.
The pseudogens
are nucleotidic sequences that do not give anymore a genic
product because of mutations.
Yours
sincerely,
Andrea
Clapasson
Ospedale S.
Martino
Genoa, Italy
E-mail:
andrea.clapasson@hsanmartino.liguria.it
