Among non-invasive urine tests, urine tests with molecular biomarkers are promising tools for diagnosing BC . However, these tests are still not well established in daily clinical routine and in the standard diagnostic workup of BC. Further evaluation of the usefulness of these biomarkers in complex clinical situations is needed before they are recommended for widespread clinical use. Considering that BC patients are often associated with haematuria, which also is the most common manifestation of other urological diseases [11, 12]. Hence, it is important to evaluate the usefulness of molecular biomarkers of BC in the context of haematuria interference.
The BTA stat test is a molecular urine test for BC that that is currently subject to the most attention. The BTA stat test specifically recognizes bladder tumour-associated antigen (hCFHrp) in urine through monoclonal antibodies. This antigenic protein is considered to be isolated from the urine of patients with BC but cannot be detected in the urine of most healthy individuals . Previous studies have compared the sensitivity of the BTA stat test and cytology detection in patients with BC diagnosed by cystoscopy, and the sensitivity of the BTA stat test was found to be superior to urine cytology and bladder irrigation cytology [17-19]. However, there is limited data on its effectiveness in real-world clinical situations. Especially its specificity under haematuria interference situations, needs further observations. In this study, we investigated the effect of haematuria on the sensitivity and specificity of BTA stat test in the clinical cohort.
Previous studies have shown that, the sensitivity of BTA stat test is between 57% and 83% . In our study, the sensitivity of BTA stat test to detect patients without haematuria bladder cancer was 80.77%, that is consistent with previous studies. If you analyse only patients with haematuria, the overall sensitivity of the BTA stat test was 97.22%. This illustrates the effect of haematuria on its sensitivity. Because of false-positives, haematuria patients may exhibit higher sensitivity. Our research shows that haematuria had a significant effect on the specificity of the BTA stat test in each group. In Non-bladder cancer with haematuria patients, the specificity of the BTA stat test was significantly lower than that without haematuria who had the same conditions. (The data show that except UTI and renal cancer group. the reason maybe is that UTI Urinary tract infections also significantly affect the specificity of BTA stat test and the sample size of renal carcinoma group was too small.) Furthermore, compared with other studies, our study showed more lower specificity. In a multicentre US study, the specificity of the BTA stat test in patients with BPH, urolithiasis and UTI was 88.5%, 50% and 76%, respectively . In this study, the specificity of the BTA stat test decreased to only 31.89% and 15.52% in patients with urolithiasis and UTI, respectively. In patients with prostatic cancer and renal cancer, the specificity of the BTA stat test was only 44.87% and 48.39%, respectively. This may be because we did not exclude patients with haematuria from our total enrolment in these data. In addition, our study found that the specificity of BTA stat test was correlated with the severity of haematuria. The specificity of BTA stat test in patients with haematuria under microscope was significantly higher than that of gross haematuria.
Our results suggested that haematuria leads to high positive rates. Considering that hCFHrp is a serum factor, the BTA stat test can possibly concomitantly detect serum proteins that cause haematuria. A study supports our conclusion; the Makito Miyake group built an experimental haematuria model. They added whole blood to BTA-negative urine samples and found that spiking BTA-negative urine samples with as little as 1 µl whole blood /10 ml urine was enough to produce a positive BTA stat test result . These evidences confirmed that the BTA stat test is very unsatisfactory for the diagnosis of BC. On the one hand, the majority of patients with BC will present with haematuria, gross or microscopic haematuria is often the first symptom in BC patients [11, 12]. On the other hand, haematuria is the most common symptom in urology patients. In many benign or tumorous urologic diseases, haematuria is often the only manifestation . Even 9% to 18% of normal individuals also have some degree of haematuria . This fact means that the BTA stat test may be prone to detect particularly high false positives in haematuria patients.
We analysed patients with haematuria symptoms in a clinical setting and found that the specificity of the BTA stat test was only 15.82% for all groups of patients with haematuria. The meaning of these data is that when only patients with haematuria symptoms who were suspected of having BC were considered, the specificity of diagnosing BC with the BTA stat test was only 15%. In addition, the proportion of BC patients with haematuria is very small, especially for patients with microscopic haematuria. Previous studies have shown that only about 1% of patients with microscopic haematuria actually have BC [10,24,25]. In this case, if the BTA stat test has such a high false-positive rate for haematuria, it will lack further directivity, and its clinical utility and benefit will be low. The cost of screening includes the cost of labelling each patient and the cost of evaluating patients with false-positive results. Adding any test to the clinical assessment will increase costs; thus, the cost-effectiveness needs to be balanced by the benefits.
Optimal screening strategies require not only identifying a method with high sensitivity in a population with significant disease prevalence, but also requires this method with reasonable specificity . The specificity of the marker plays a key role because more patients with false-positive results correlates with needing additional “unnecessary” tests. Our results suggest that the BTA stat test cannot achieve ideal effective specificity and that using it to screen and monitor for BC may lead to “unnecessary” costs. Therefore, BTA stat test is not recommended for screening or diagnosing BC in patients with haematuria.
In addition, in case of follow up of urinary tumour markers, negative predictive value is also very important if our goal is to avoid a more invasive cystoscopy based on the urinary tumour marker report. In our study, the negative predictive value of BTA stat test was 97.09%, which is similar to the results of previous studies. Our study also showed that the negative predictive value of BTA in patients with haematuria was significantly higher than that in patients without haematuria, and the difference was statistically significant (P＜0.05). Nevertheless, we must note that because the negative predictive value is affected by the prevalence, even if the diagnostic performance is very poor, this value can be as high as 90% or more when the prevalence is relatively low. At this time, it is not objective for us to use the negative predictive value to measure the diagnostic value of diagnostic experiments. After identifying high-risk groups, negative predictive value can play its greatest role, but this requires large-scale prospective studies to determine the actual prevalence in high-risk groups. If the prevalence is still low in high-risk groups, then the cost and actual benefits of screening need to be considered. Further studies can compare and analyse the specific costs involved in the clinical practice of qualitative urinary tract testing. However, there are no available data on this problem.
A variety of biomarkers for evaluating bladder cancer have been developed, including protein-based and gene-based biomarkers. As with BTA, the use of the protein marker NMP22 also has been hampered by haematuria [27-28]. It is worth noting that these results did not indicate that the high false positive of protein-based makers in patients with haematuria are directly caused by red blood cells in the urine. It may also be that the factors that promote haematuria may also promote tumour cell shedding, thereby increasing the positive detection rate of these makers. Hence, for protein-based biomarkers, it needs to be tested under specific circumstances. Gene-based detection of bladder cancer is much better for performance under haematuria interference, such as UroVysio test and Cxbladder test [29-30]. But these testing methods are far more complex, and the high cost is the biggest obstacle to their widespread use.
There are some limitations to our study. There is too less a number of patients in T3, T4 category, undifferentiated cancer groups. The sensitivity of 100% in these patient groups may not be statistically significant. the sample size of Renal cancer group is small, which may also cause some bias. We Providing and retaining these data so that readers allow readers to evaluate the sample size and clinical data.