PONE-D-24-04363Enhancing clinical decision-making: Sysmex UF-5000 as a screening tool for urinary tract infections in childrenPLOS ONE

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: Yes

Reviewer #5: Partly

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: No

Reviewer #3: Yes

Reviewer #4: No

Reviewer #5: Yes

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Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: Yes

Reviewer #5: Yes

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Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: No

Reviewer #5: Yes

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5. Review Comments to the Author

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Reviewer #1: This is a very interesting study testing the Sysmex UF-5000 as a screening tool for UTI in children.

Zhe authors included 4445 patient informations and compared the BACT and WBC counts received by the UF-5000 with the measured data in the laboratories. The bacterial counts in the laboratory was classified as „no growth“, <10*4 CFU/ml, 10*4-10*5/ml, and >10*5/ml. The authors calculated for each parameter the usual statistical parameters, like sensitivity and specificity, negative and positive predictive values etc. Depending on the Cut-off BACT they could calculate these statistical parameters with the results, how many urine cultures would have been most likely unnecessary. Because they also could differentiate with high probability between most likely GN and GP cultures, these results would also be important if empiric antibiotic therapy was to be chosen. The authors compared their results with other studies as well, however, most of them were performed in adults. They also discussed well the limitations of their own study.

Overall, the study was well performed and presented. I only have (minor) comments/questions. Unfortunately the lines of the manuscript are not numbered.

1. Concludions: I like that the authors write Gram usually with capital letter, because it is the name of a person. In Conclusion it should also be written with capital letter.

2. Urine culture and identification of microbes.“If there was sterile growth“. Although the authors used 10 µl for urine culture, also in case of no growth, one cannot say ir is sterile. Therefore, better: „If there was no growth“.

Table 2. Typing error: Tocal? Maybe should read Total. It was used 3 times.

Otherwise I have no further comments.

Reviewer #2: Urinalysis is a very important issue in most laboratories worldwide. In the last decades automated urine particle analyzers have reduced microscopic examinations and unnecessary cultures. In their study, Liu P et al. investigated the performance of the UF-5000 fluorescence flow cytometer especially in pediatric urinary tract infections.

This report has some merit because of the pediatric study population. The manuscript is well written, however, before publication in this journal some minor points should be considered:

• Abstract (methods): “We analyzed 4445 patient information of children….” This sentence should be rewritten in a better and more informative way.

• Ethics statement: “And began accessing data on December 29, 2023. The author had access to information that could identify individual participants during data collection…” This part should be rewritten in a better English.

• Results/Microbial species: “C. tropical” should be spelled out to “Candida tropicalis”

• Table 1: “Proteus mirabili” should read “Proteus mirabilis”

• Results/Diagnostic performance of UF-5000: “Excluding samples from the fungus culture and the <104 CFU/mL group, an ROC curve…” should read “…, a ROC curve…”

• The “limitations” should be mentioned before the conclusion.

Reviewer #3: The manuscript “Enhancing clinical decision-making: Sysmex, UF-500 as a screening tool for urinary tract infections in children” is interesting and confirms/validates in a large cohort, previous findings on the utility of flow cytometry for detection of UTI. Several studies have evaluated the performance of the UF-5000 in different kinds of patient cohorts but as this study is the first on a large cohort of children, it brings new knowledge to front. The paper needs some revision before publishing.

DETAILED COMMENTS

Q1: Abstract, Results. The author mentions that unnecessary culture could be avoided in 28.1%. Are there a reason for presented the numbers with 3 digits? Why not say 28%. I hardly think the estimates is that precise?

Q2: Abstract, Conclusion. Cultures screened with UF-5000 showed superior results in identifying…superior in comparison to what? I don’t think you mean compared to urine culture? Or do you mean compared to previous flow cytometry models like UF-1000 or compared to Urine stricks? The UF-5000 may be faster than culture but not better. It may also be better that other fast screening methods.

Q3: Introduction/discussion. The authors mention that rapid screening test for UTI is needed for children. But there is nothing mentioned about urine dipsticks that are ruinously used in many settings for rapid screening, including in children >2 years of age. Is that because the dipsticks are not used at this children’s’ hospital? It may be worth mentioning that there are a lot of rapid screen test on the marked, but they do show inadequate performance compared to culture.

Q4: Urine Culture: Inoculation involved using a calibrated loop to apply 10 µL culture. It is common to use a 1-μL inoculating loop, so can you elaborate on the choice of the 10 µL loop? It may be a good point to include in your discussion as many of the studies you compare uses 1 µL loop cultures and therefore you may not compare to the same culture standard.

Q4: Urine culture. BACT counts≥104CFU/mL should be changed to BACT counts≥104 CFU/mL. Do the sentence BACT counts ≥104CFU/mL (when symptomatic) where considered positive, mean that samples with ≥104CFU/mL where excluded if the patient did not have any symptoms? I don’t think you can exclude culture positive samples from the dataset, at least not without mentioning this a an exclusion criteria. Also how where ≥103CFU/mL classified? As negative? You may stick to the recommended cut-off urine cultures in children at ≥104 CFU/mL.: 1999. Practice parameter: the diagnosis, treatment, and evaluation of the initial urinary tract infection in febrile infants and young children. American Academy of Pediatrics. Committee on Quality Improvement. Subcommittee on Urinary Tract Infection. Pediatrics 103:843-852

Q5: Results UF-5000 BACT and WBC count and Figure 1. You mentioned in caption to fig.1 that fungi are excluded. Why is that? Are fungi defined as culture negative or positive? You need to define this or explain the rationale about excluding them. Fungi is a non-bacterial UTI.

Q6: You identified 513 samples with significant growth. I think you should use the same term in the manuscript for culture positive. So may change the sentence to 513 culture positive samples.

Q7: Diagnostic performance of UF-5000. Again rationale for excluding samples with fungi.

Reviewer #4: This study investigated the performance of Sysmex UF-5000 analyzer parameters for screening urinary tract infection (UTI) in children. I believe the manuscript should be rejected due to the following reasons:

1、 The manuscript is poorly organized and its readability needs to be extensively improved.

2、 The language quality does not meet the publication criteria of PLoS ONE.

3、 The authors should provide more details about the inclusion and exclusion criteria for the patient enrollment.

4、 I suggest the authors use a flowchart to depict participant selection.

5、 How to handle duplicated participants?

6、 The type of data collection (retrospective or prospective) should be reported.

7、 The sample sizes of UTI and non-UTI were not reported.

8、 In table 2, the rate of missed diagnosis should be reported.

9、 The novelty and strength of this study were not well discussed in the discussion section.

Minor comments

1、The upper limit of AUC’s confidence interval should not exceed 1.

2、The 95% confidence intervals for sensitivity and specificity should be reported

Reviewer #5: The authors report on the performance of the Sysmex system for diagnosing urinary tract infections among children from one hospital in China. The diagnostic method is valid and can reduce time to result and laboratory workload by reducing the number of unnecessary urine cultures. To better understand and interpret the findings, the authors should add more detail on the setting, study design and patient population. Further comments below.

Introduction

- Improper collection is more likely to lead to contamination and hence false positive results

- Comment on the use of dipstick test for UTIs in children (given that it also provides rapid results and is very cheap)

- When introducing Sysmex, please add the manufacturer and location

- Explain to the reader by which mechanism can the Sysmex differentiate between Gram positive and Gram negative organisms

Methods

- “If there is sterile growth” please rephrase to no growth or similar

- Describe what symptoms were considered and how the data were collected

- Add some information about where the study was conducted including some background about the setting, on the study design, prospective or retrospective, and on the approach for enrolling patients, alternatively whether data were obtained from medical records. Also include some data on the patient population to add with the interpretation of findings (enterococci were relatively common, Candida is usually considered a contaminant – were a considerable proportion of patients immunosuppressed)

- Data analysis: state in the text for which two parameters Sensitivity and specificity were computed

Results

- Add percentages in the first paragraph

- No need to list the SE for the ROC curve AUC

- Explain in the methods how the “best” cut-off was selected for calculating Sensitivity and specificity

- Would a combination of using WBC by Sysmex and Bacterial count improve test performance.

- “… based on the gold standard of midstream urine cultures, the total compliance rate of UF-5000 for distinguishing UTIs is…” Please note that when considering your definitions in the methods section, not all growth represents a UTI (some may be asymptomatic bacteriuria). If necessary correct for clarity. Also please clarify what is meant by “compliance rate”

- Explain what “unclassified flags” are

Discussion

- The yield of urine cultures is quite low. Comment in more depth on possible reasons (in adults yield can be higher than 40% reaching 70-80%). Similarly the prevalence of Gram-negatives was relatively low (one would expect that more than 60% of samples would have Gram negative growth) – comment on possible reasons.

- Replace Enterobacteriaceae with Enterobacterales

- When setting cut-off values for sensitivity and specificity consider that these can also be population-dependent as well as depend on the strategy the authors decide to use for setting the cut-off (better sensitivity vs better specificity vs Youden). These might explain the slight differences between studies and there might not be a “best” cut-off in this scenario (results apply to this specific study, as you discuss in the next sentence).

- “We recommend a BACT count cut-off of 7.8/uL for screening out patients with negative cultures, especially if they have no clinical symptoms of UTI.” – should these patients be tested at all if asymptomatic?

- Include the limitations before the conclusion

Tables and Figures

- Table 1: replace ratio with proportion, italicise species names, list in the footnote what other Gram positives and Gram negatives were isolated, also for other Fungus (other fungi); Proteus names is misspelled, consider that Candida can be a contaminant

- Table 2: add space between number and parantheses. There is typo for specimens in the first cell also for “total”

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Reviewer #1: No

Reviewer #2: No

Reviewer #3: No

Reviewer #4: No

Reviewer #5: Yes: Ioana Diana Olaru

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Enhancing clinical decision-making: Sysmex UF-5000 as a screening tool for bacterial urinary tract infections in children

PONE-D-24-04363R1

Dear Dr. Xin Lv,

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Kind regards,

Eleonora Nicolai, PhD

Academic Editor

PLOS ONE

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