Methods: One hundred and fifty hard-working agricultural farmers from high-prevalence area for CKDu (Madawachchiya) were screened three times for proteinuria; 66 proteinuric and 21 non-proteinuric were identified as the baseline classification. Selected individuals were analysed further for creatinine, protein and cystatin C in urine and creatinine, cystatin C in serum. Urine protein-to-creatinine ratio (UP/UC) was calculated.
Results: Based on creatinine and cystatin C cut-off levels in serum, individuals were classified as high or normal. Diagnosis of two functional markers (creatinine and cystatin C) were evaluated using receiver operating characteristic (ROC) curve and in terms of sensitivity and specificity using UP/UC as the baseline. Creatinine and cystatin C-based eGFR (estimated Glomerular filtration rate) levels were calculated, and Pearson's correlation coefficient was determined between different eGFR measurements using UP/UC. Mean (SD) UP/UC ratio, serum creatinine, and serum cystatin C levels of the proteinuric subjects were 129.0 (18.4) mg/mmol, 1.35 (0.39) mg/dL, 1.69 (0.58) mg/L. For non-proteniuric individuals, the results were found to be 14.4 (2.28), 1.22 (0.40) mg/dL, 0.82 (0.25) mg/L. The ROC analysis showed excellent accuracy in using cystatin C for identifying proteinuric patients than creatinine area under the curve (AUC): 0.9675, P < 0.001). Cut-off points were identified as 1.015 mg/dL for serum creatinine and 0.930mg/L for cystatin C. Furthermore, cystatin C based Hoek formula showed the better correlation (0.635, P < 0.001) with UP/UC compared with creatinine based modification of diet in renal disease (MDRD) formula.
Conclusion: The study showed elevated serum cystatin C in patients with persisting proteinuria compared with non-responding serum creatinine. Moreover, cystatin C-based eGFR equations were more accurate to determine the kidney function than serum creatinine in proteinuric patients who are vulnerable for CKDu in high-prevalence areas.
CASE PRESENTATION: An army officer who returned from Malaysia in October 2016 was found to be positive for Plasmodium both by microscopy and rapid diagnostic test (RDT) by the Anti Malaria Campaign Sri Lanka (AMC) during his third visit to a health care provider. Microscopy findings were suspicious of P. knowlesi infection as the smears showed parasite stages similar to both Plasmodium malariae and Plasmodium falciparum. Nested PCR at AMC confirmed Plasmodium genus, but not the species. In the absence of species confirmation, the patient was treated as a case of P. falciparum. The presence of P. knowlesi was later confirmed by a semi-nested PCR assay performed at the Environmental Health Institute, National Environmental Agency in Singapore. The parasite strain was also characterized by sequencing the circumsporozoite gene. Extensive case investigation including parasitological and entomological surveillance was carried out.
CONCLUSIONS: Plasmodium knowlesi should be suspected in patients returning from countries in the South Asian region where the parasite is prevalent and when blood smear results are inconclusive.