Dip-S-Ticks Leptospira rapid text (PanBio)
Fairly easy to use, this test does, nevertheless, require a minimum amount of technical material (precision
pipette, water bath or thermostatically controlled 50° heating block). It can, then, be used on sites with
limited equipment but cannot be conducted outside a laboratory. It is easy to read the results which have
judiciously been made quantifiable by a series of 4 increasing antigen solution spots (guide of 0 to 4 arbitrary
units, with the result considered positive at 2 or more). After testing, the dried strips can be kept for later
readings, as the colours appear to remain stable for a long time (more than a month in our experience to
date).
The specificity of the response is excellent (100%), since no cross reactions were uncovered with the nonleptospirosis
disease panels. This results matches an evaluation conducted recently in Hawaii which gave a
specificity of 95% [2].
Sensitivity was evaluated at 80%. Four samples which had been positive in the micro-agglutination test gave
a response which was zero or less than 2 with the Dip-S-Ticks: 1 sample that was positive at 1/400th for the
Panama serogroup, another at 1/12800th for the Icterohaemorragiae copenhageni serovar and 2 sequential
samples from a single patient showing a seroconversion for the Australis serogroup (score on the late sample
at 1.5, whereas the MAT is positive at 1/3200th ). The other three seroconversion panels were correctly
identified. It was noted that there was a reaction, sometimes strong, at the beginning of the infection at the
time when the MAT shows coagglutination for several serogroups, including non-pathogens such as Patoc
(see Table III, patient GR).
The negative predictive value of this reagent was not 100%, but just 89.5%. When used as a front-line
screening test, all negative tests in spite of a clinical context resembling leptospirosis, would have to be
retested by another technique - especially if the sample was taken soon after the symptoms first appeared. In
Smits et al’s evaluation (1999 [1]) of a first generation Dipstick, they found sensitivity to be 61% for early
samples (illness of less than 10 days) and 87.4% for the latest samples.