The Parameters and Results Displayed in Sysmex UF-100 - Assignment Example

Viva2 Tell us how Sysmex UF-100 acts. Every urine specimen is assigned a bar and the machine identifies the specimen by it. Then, 800 L of uncentrifuged urine is aspirated by the machine automatically. This specimen has crystalline content like urates. This is diluted 4 times to dissolve this and other crystalline content. This uses a dilution buffer to do this. This dilution buffer stabilises the osmotic pressure to enable impedance measurement. The sample is heated to 37 degrees to dissolve the amorphous cystals like urates. Then carbocyanine and phenanthridine are used to stain the urine. This urine enters the flow cell to do a flow cytometry. 2. What are the parameters that are measured in Sysmex UF-100 The urine conductivity is measured. The formed elements or cells are analysed by electrical impedance for volume, by forward light scatter for size. To enhance the contrast fluorescent dyes like phenanthridine is used to delineate DNA and carbocyanine is used to stain the cell membranes. The cells will naturally vary in their sizes, shapes, volumes, and staining characteristics. Depending on these criteria, the cells and formed elements will be categorized in multidimensional space. 3. How are the results displayed in Sysmex UF-100 The results in Sysmex UF-100 are displayed in scattergrams on a screen and a printout of the results can be taken to be analyzed. 4. Tell us about its utility, how reliable is the test method Yes it is a very reliable method of complete automated urinalysis. It can perform sensitive quantitative microscopic urinalysis completely automatically without the intervention of an operator or attendance of an analyst. Thus, this is capable of accurate and precise quantification of microscopic elements in urine with no interaction. In studies, it has been proved that the results bear concordance with other studies, such as, automated Dipstick reader. 5. Can this replace conventional microscopic analysis No, conventional microscopic analysis cannot be substituted by Sysmex UF-100. Microscopic sediment analysis combined with UF-100 can improve the quality and productivity of urinalysis. Also, this can greatly reduce the number of specimens sent for microscopic examination of urine specimens. 6. Can you summarize the benefits of UF-100 Combined analysis by a strip reader and automated counting can reduce the number of urine microscopic examinations, can reduce turn-around times, can reduce manual labour, thus can attend many patients who can be treated rapidly in case of an established UTI. 7. Is it effective in diagnosing UTI Sure. Studies compared to other procedures of microbiologic evaluation, Dipstick tests, and microscopic examination when placed side by side with clinical data from the patients reveal that UF-100 dependably diagnose UTI in adult patients. 8. Is it an absolute information No, there are other studies done by Zaman et al in 2001, they opine that UF-100 alone or in combination with strip tests does not reliably diagnose UTI in patients. 9. Is it not a little confusing Yes a little. There are many studies done on the effectiveness of UF-100. Three different kinds of opinion emerged. One, Sysmex UF-100 alone is a dependably independent diagnostic tool that can perform precise and accurate urinalysis. Second, Sysmex UF-100 alone is not completely effective, it needs parallel tests like urine strips can be more accurate so that there is less need to perform urine microscopic analysis. Third, Sysmex UF-100 alone or in combination not enough specific to be a safe screening method for urine samples for UTI. What transpires is, there is considerable variation in sampling, methodologies, analysis, and conclusions for consistency and validity of these tests. 10. Can you support your proposition Manoni et al performed a rigorous study in 2002. It was extensive. This study specifically examined the strength of UF-100 in diagnosing UTI in adults. They sampled a wide range of age groups of 18 to 78 years, of whom 57% were females and 43% were males. Majority of the samples were collected by clean-catch midstream urine collection method in sterile containers. A 10% of the samples were collected by catheter sampling. A 12-mL aliquot was transferred into a test tube and examined within the hour to avoid delay-induced errors. 11. How can you say this age range is representative one UTI is more prevalent in females, especially until the age 50. The mean age of this population was 56.4; with females constituting the better half, we can say this was a representative sample. 12. Tell us about the methodology of this study. This study utilized a rigorous methodology. They utilized different analytic methods to conclude on this issue. They utilized both culture and non-culture methods of urinalysis on the specimen for more accurate results. The Dipstick analysis was performed on the urine samples using URIFLET strips and super Aution automated reflection photometry. To identify bacteria and leukocytes, these specimens were tested in UF-100 analyzer. 13. How could the analyzer detect UTI The cutoff value for bacteriuria was set at 100,000 bacteria/mL and that of leukocyturia was set at 25 cells/mL. 14. How could you establish that the UF-100 was reading right These specimens were examined microscopically. For microscopic analysis, 10 mL of each specimen was centrifuged at 400 gyrations for 10 min, and after the centrifugation 9.5 mL of supernatant was discarded leaving the sediment. This was then microscopically examined. 15. Can you ensure that any examiner would get uniform reading in all the fields Correct, the bacterial presence should not be uniform; for this reason and to account for partial or incomplete centrifugation, at least 20 random microscopic fields were examined at X400 high-power field by the same observer. 16. Why same observer This is to eliminate the factor of interobserver variability. 17. Then Then the mean number of cells per HPF would be calculated. 18. Can you point to a gap here Yes, this study did not include examination in the low-power field to corroborate the findings in the HPF. 19. Did they identify the bacteria How These specimens were inoculated on Agar plates using 0.001 mL calibrated loops within 4 hours of specimen collection. This was to forestall the bacterial growth in the specimen that may contaminate the culture. 20. What was the culture media used They used both selective and nonselective culture media. For selective they used McConkey (McC) agar and colistin-nalidixic acid blood (CNA) agar, and for nonselective, they used cystine lactose electrolyte deficient agar (CLED) media. The cultures were left for 24 hours at 37 degrees Centigrade, and they quantified the culture plates after 24 hours of growth. 21. How did they quantify the culture results In the CLED plates, colonies from 0 to 10 (i.e. under 10,000CFU/mL) was considered negative, colonies from 11-100 (i.e. from 10,000 - 100,000 CFU/mL) was considered moderate, while over 100 (100,000 CFU/mL) was considered significantly high. 22. What did they do about the significantly high colony growths They performed a biochemical testing and sensitivity to antimicrobial drugs using DADE microscan automated systems. 23. What is DADE The name DADE stands for Dade Behring; this system is developed by them for clinical diagnosis of UTI. 23. Tell us about the statistical analysis of this study. Of the 2010 subjects selected, UTI was diagnosed in 26.32% of cases, and this result was integrated with results obtained from UF-100 and strip reader, microscopic and sediment analysis. 24. What was the conclusion The authors concluded that UF-100 cytometer has a sensitivity of 0.94, specificity of 0.93, positive predictive value of 0.83, negative predictive value of 0.98, and corrected classified incidence of 0.93. 25. Please explain this. Of the 2010 specimens examined, the UF-100 cytometer only showed 29 false negative results and 102 false positive results. These 29 false negative cases, 20 samples were from patients with UTI but with low bacterial count that yielded false negative results in CLED agar. Actually, hence there were only 9 cases of true false negative results with samples having significantly high bacterial counts. In the 102 false positive results, 35 cases were due to presence of polymicrobial flora indicating contamination of the urine samples, and 59 cases were due to detection of presence of pus cells in the urine but without UTI. However, of these 59 cases, 51 were females where there is a fair chance of contamination with the vaginal mucosa, hence their source was questionable. So to summarize, the UF-100 failed only in 20 or 0.99% cases. 26. What do you want to mean I want to mean that this study clearly establishes the effectiveness of UF-100 as a precise diagnostic tool for detection of UTI in adults. 27. You said something about Zaman. Yes, Zaman et al performed a similar study but came up with a conclusion opposite to this. The sample in Zaman's study was not that extensive, but the methodology was basically the same. For this study, the patients consisted of inpatients and outpatients of a tertiary care centre. They included 534 patients with 51% females and 49% males. 28. Describe the methodology. The cultures were developed before any test. The cultures were performed by inoculating 10l of uncentrifuged and well-mixed urine on blood agar and MacConkey agar plates and incubating them aerobically at 36C for 24 h. After the culture was inoculated, the urine was examined with an automated strip reader. The reader used was Uriflet S9 UB urine strips. Then, the sample was analyzed with UF-100. The cut-off values for bacteriuria and pyuria were set at 20/L for pyuria and 2,750/L for bacteriuria. In the culture study, bacterial count of less than 10,000 CFU/mL was marked negative and above 100,000 CFU/mL was considered significant for UTI. 29. Tell us about the statistical analysis and implication of the results. The statistical analysis was not elaborately carried out. The results were presented in the form of table comparing three methods of parallel testing. Thus, UF-100, strip reader, and microscopic analysis of the specimen were compared. With the cut-off values set at 20/L for pyuria and 1000/L for bacteria, the highest specificity obtained was 99.3% and positive value was calculated to be 88.9%. But this again produced a high count of false negative results of 128. But when the results were combined from UF-100 and strip reader with the same cut-off values and leukocyte esterase values for the strip reader, the highest negative predictive value (87.5%) and the lowest false-negativity rate (4.3%) were obtained. 30. How many cases This translated into a total of 24 false negative cases. Of these, 9 cases had significantly high colony count. 31. What does this imply According to the authors, missing out 9 cases of this study population of 534 patients implies unsafe testing since this is significantly great on any study and this can have effect on patient morbidity. Thus it can be concluded that alone or in combination with a strip reader, UF-100 fails to accurately and precisely diagnose existence of UTI, hence not suitable for urinalysis. 32. Is this a sufficient logic No, these 9 subjects represent statistically only 1.6% of the total sample size, specifically when they are comparing the results with microscopic analysis. The microscopic analysis can be bugged with observer defects, and there is no gold standard for urinalysis testing. 1.6% is an acceptable percentage of false negativity for any testing method, hence the interpretation, in my opinion, is faulty, and my opinion in this regard is supported by many other studies which have concluded that UF-100 analyzer is consistent, precise, and accurate to diagnose UTI. 33. What ideally should be the laboratory method of diagnosis of UTI The laboratory diagnosis of UTI should be timely without delay. Microbial diagnosis and sensitivity studies are important adjuncts for institution of therapy. Manual methods have the disadvantages of delay, and urine sediment analysis is not completely flawless and even not considered as the gold standard of urinary diagnostics. 34. Criticize conventional diagnostic procedures. Conventional diagnostic procedures comprise of analysis by test strips, and if indicated by the test strip results a full scale urinary sediment microscopy. It is not flawless, since there is interobserver variability in results, it is time consuming and labour intensive. 35. What would then be the preferred method for diagnosis of UTI The method for collection of urine specimen should avoid contamination; in this light suprapubic aspiration of urine specimen is the best, but rarely followed due to invasiveness and risks. Non culture methods of testing include Gram staining of both centrifuged and uncentrifuged specimens, direct observation of bacteria in the urine, nitrite tests, and leukocyte esterase tests. Culture tests will detect the bacteria in a suitable culture medium. Then the semi-automatic and automatic methods were devised. 36. Tell us about some semi-automatic methods. These were early attempts at automated urinalysis. These machines were Yellow IRIS, UA-1000 and UA-2000. Yellow IRIS specifically yielded comparable results with visual microscopy, more often in the lower concentration range. 37. Briefly tell us about Yellow IRIS. The mucous strands are first removed. A dye is added to the urine. The stained urine is passed through an optical pathway. A strobe lamp interrupts the fluid and particulate motion, and this is captured in a coloured video camera. The resultant images are differentiated based on their standard lengths, and the result is analyzed by a trained analyst. UA-1000 and UA-2000 are better that IRIS since they have better resolution with the use of a colour CCD camera. 38. Then what is UF-100 you were talking about This is a completely automated system for diagnostic urinalysis with no necessity of manual analysis. This works on the principle of argon flow cytometry. This can recognize particles and cells in the urine. This has been shown to be a precise, accurate, and effective automated diagnostic urinalysis tool. 39. Summarize the different opinions about UF-100. UF-100 should not be considered as a substitute of conventional microscopic sediment analysis. This if combined with an automated Dipstick reader can improve the numbers of specimens examined, and thus can reduce the numbers of microscopic analyses, since only those found positive by the two methods combined will be subjected to microscopic examination. This will also reduce delay, turn-around times, and manual labour and hence the number of specimens ultimately subjected for microscopic analysis. Most studies have supported the efficacy, safety, specificity, and usefulness of UF-100. Even the isolated case, which did not support this view had only 1.6% false negative tests. 40. What is your final conclusion Automated laboratory tests for diagnosing UTI are not only better, they are far superior to manual testing. It has the advantage of time and rapidity, which is the main concern of the clinical people responsible for the treatment of patients with suspected UTI. The delay can itself compromise the quality of the study. The automated system, although not designed to replace the manual microscopic studies of the sediments in the urine, may effectively select the cases that would need microscopic examination. Apart from this, automated system can indicate the samples that would need culture very quickly. In combination with other methods of studies is fairly accurate, precise, and specific in diagnosis of UTI. The false negative rates are also low. If the results can be combined with other studies, automated UF-100 tests can reduce diagnosis time, manual labour, and turn-around time, and this should be preferred method of present-day clinical diagnosis. 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