PCR for the diagnosis of abdominal angiostrongyliasis in formalin-fixed paraffin-embedded human tissue.

To date the diagnosis of abdominal angiostrongyliasis (AA) depends on the histological identification of Angiostrongylus costaricensis (AC) in surgical specimens. However, microscopic evaluation is time consuming and often fails in identifying the parasite. We tested whether PCR might help in the diagnosis of AA by identifying parasite DNA in formalin-fixed paraffin-embedded (FFPE) tissue. We used primers based on DNA from Angiostrongilus cantonensis. Four groups of FFPE intestinal tissue were tested: (1) confirmed cases (n = 20), in which AC structures were present in the target tissue; (2) presumptive cases (n = 20), containing changes secondary to AC infection in the absence of AC structures; (3) negative controls (n = 3), consisting of normal colonic tissue; and (4) tissue affected by other parasitoses (n = 7), including strongyloidiasis, ascaridiasis, schistosomiasis, and enterobiasis. Most lesions of confirmed cases were located in small and/or large bowel (90%), as compared with presumptive cases, in which 70% of lesions were in appendix (P = 0.0002). When confronted with cases of other parasitoses, PCR showed sensitivity of 55%, specificity of 100% and positive predictive value of 100%. In presumptive cases PCR was positive in 4 (20%). All specimens from negative controls and other parasitoses were negative. In conclusion, the PCR technique showed intermediate sensitivity and optimal specificity, being clinically relevant when positive for abdominal angiostrongyliasis. It allowed a 20% gain in diagnosis of presumptive cases. PCR might help in the diagnosis of abdominal angiostrongyliasis, particularly when the pathologists are not experienced with such disease.

Erythrocyte L-arginine uptake in peritoneal dialysis patients changes over time.

During long-term exposure to continuous ambulatory peritoneal dialysis (PD), the characteristics of the peritoneal membrane may be altered. The substrate for nitric oxide synthesis is L-arginine, which may enter cells via the y+ and y+L transport systems. Peritoneal membrane characteristics may depend on vascular function and the L-arginine-NO pathway. Maximal capacity for L-arginine transport is higher in patients with a lower dialysis adequacy index. Our aim was to evaluate erythrocyte L-arginine uptake in PD patients at the start and end of a 3-year interval. Our longitudinal study evaluated 8 stable patients on PD who were not using NO donors and who had been free of peritonitis for at least 1 month. Uptake of L-arginine was measured in 2003 and again in 2006. Maximal transport capacity (Vmax, in micromoles per liter-cells per hour) and half-saturation constant (km, in micromoles per liter) were measured in erythrocytes using 14C as a marker and N-ethylmaleimide as inhibitor of the y+ system. For the years 2003 and 2006 respectively, mean +/- standard deviation for total L-arginine uptake Vmax was 749 +/- 182 micromol/L-cells/h and 1146 +/- 365 micromol/L-cells/h (p = 0.016, paired t-test),for y+L Vmax was 180 +/- 58 micromol/L-cells/h and 515 +/- 142 micromol/L-cells/h (p = 0. 002), and for y+ Vmax was 556 +/- 177 micromol/L-cells/h and 662 +/- 267 micromol/ L-cells/h (nonsignificant). The total y+L and y+km were not significantly different. The L-arginine maximal uptake capacity in erythrocytes increased after 3 years of PD treatment. These findings agree with the suggestion of an association between y+L activity and dialysis adequacy or uremia toxicity. Peritoneal membrane characteristics may depend on vascular function and the L-arginine-NO pathway.