Standardisation of a two-site PTH immunoradiometric assay using various solid phase formats.

Background & objectives: Estimation of parathyroid hormone (PTH) levels is important in the management of metabolic bone disorders. Here we describe a simple, sensitive and specific second generation immunoradiometric assay (IRMA) to detect intact PTH levels using different solid phase matrices. Different methods for immobilization of antibodies have also been evaluated. Methods: Experiments were carried out with physical adsorption of antibodies, covalent coupling using 2 per cent glutaraldehyde and N,N`carbonyldiimidazole. In all cases, antibodies raised against C-terminal were used as solid phase agent. Detector antibodies were N terminal antibodies that were radio-iodinated with 125I followed by gel purification. Several of the antibodies coupled to various solid phase matrices were incubated with PTH standards and the detector antibody as well as the commercially available tracer from DiaSorin kit to identify a suitable match pair. Results: The best pair was polyclonal C-terminal PTH antibody along with the kit tracer from DiaSorin with regards to antibody coated to magnetic cellulose particles. Among the various antibodies and the solid phases evaluated, the best assay was obtained with the matched pair of antibodies (70×G67 and 70×G68) from Fitzgerald immobilized on polystyrene tubes. The polyclonal antibody against C-terminal PTH was chosen as the capture antibody and 125I labelled polyclonal antibody against N-terminal PTH as the tracer. The sample values obtained in the antibody coated tubes were comparable to those obtained using a commercial kit. Interpretation & conclusions: The results indicated the feasibility of adopting this system for further development into a PTH IRMA for regular production as there is no indigenous kit available for intact PTH.

Viability of Mycobacterium leprae in lepromatous patients after five years of dapsone monotherapy supplemented with two years of multidrug therapy.

Eleven lepromatous leprosy (LL) patients with a bacterial index (BI) of three and above who had undergone two years of multidrug therapy (MDT) and yet had positive skin smears at the end of treatment were chosen for this study. Biopsies from the skin and lymphnodes were histopathologically evaluated for the presence of granulomas and M. leprae. M. leprae isolated from the skin and lymphnodes were inoculated into the foot-pads of normal mice to test their viability. On histopathological examination of the biopsy specimens, it was found that granulomas and M. leprae were present in the skin and lymphnode biopsies of all patients except two, in whom, although granulomas persisted, M. leprae were not found in skin biopsy specimens. No growth was obtained in the foot-pads of mice inoculated with organisms isolated from skin and lymphnode biopsies of all 11 patients indicating a near complete bacterial kill. That would account for the extremely low relapse rates reported until now in LL patients who had undergne two years of MDT.

Limited duration acedapsone prophylaxis in leprosy.

A randomized controlled chemoprophylaxis trial was carried out in Madras city using 560 disease-free household child contacts of 264 multibacillary cases as study subjects. In the study, 13 cases were diagnosed among 280 contacts who received 3 injections of acedapsone at 10 weeks interval as against 30 cases among 280 contacts who had the same number of placebo injections, during the follow-up period of 225 weeks. The difference in the incidences in the two groups was statistically significant. (X2 6.45; P less than 0.02). The protection due to the limited duration of acedapsone prophylaxis was 56.7 percent. There were no cases of multi-bacillary leprosy in either group. The efficacy of prophylaxis was significant in male children over 9 years of age and female children in the age-group 1-8 years. The other prognostic factors like the infectivity status of the index cases in the household and the duration of exposure to them could have possibly influenced the effectiveness of prophylaxis in preventing progression from infection to clinical disease among the subjects studied. Their effects could not be assessed in this study.