[Comparison between centrifugation and sedimentation prior to cultures in the isolation of cytomegalovirus in the urine of renal transplant recipients].

BACKGROUND

To compare the capacity of conventional centrifugation and spontaneous sedimentation to detect the presence of cytomegalovirus (CMV) in urine samples.

MATERIAL AND METHODS

We studied urine samples from 45 renal transplant recipients. After decontamination half of each sample was centrifuged (1,500 rpm for 10 minutes) and the other half was allowed to sediment at room temperature for 30 minutes. From the supernatant of each of these 250 microliters was inoculated in a shell-vial (MRC-5). Cultures were incubated for 48 hours at 37 degrees C and stained by an indirect immunofluorescence assay. The samples considered totally toxic were re-inoculated after dilution 1:1 with maintainance medium.

RESULTS

Of 845 urine samples analyzed, 743 (88%) were negative and 102 (12%) positive. 66 (7.8%) were considered toxic: 35 (4.1%) partially toxic and 31 (3.6%) totally toxic. Of the centrifuged urine samples 86.2% were positive against 98% of the sedimented samples (p = 0.004). Of the 31 samples considered totally toxic, 17 (2.2%) corresponded with negative urine samples and 14 (13.7%) with positive samples. Off these, 12 (85.7%) were detected in centrifuged samples and 2 (14.3%) in sedimented samples (p = 0.001).

CONCLUSIONS

The percentage of toxicity in the urine samples was low (7.8%) which does not seem to suggest the need for systematic dilution of all samples. The sedimentation process enabled us to detect a greater number of urine samples positive for CMV with a lower rate of toxicity of the monolayers. The use of this process would reduce the number of samples requiring reinoculation.