Figure 1: Proposed decision tree for a non-invasive, biomarker-based diagnostic approach in chronic kidney disease (CKD). Based on current scientific literature, available prognostic and predictive biomarkers for supporting CKD management have been combined to provide guidance for their application. The figure shows the available biomarkers and their potential uses for specific diseases. If this decision tree does not lead to a definitive diagnosis, additional biomarkers—particularly in rare diseases—should be considered depending on the clinical presentation. If a definitive diagnosis and sufficiently reliable treatment recommendations cannot be derived, the invasive diagnostic approach via kidney biopsy remains the last option.

Acute kidney injury (AKI) caused by circulatory problems can usually be diagnosed reliably based on the patient's medical history. Characteristic imaging features also allow for the diagnosis of autosomal dominant polycystic kidney disease (ADPKD), as well as obstructive kidney diseases such as congenital urogenital tract obstructions (CAKUT). In structural kidney diseases not caused by diabetes or hypertension, the next diagnostic step is the differential diagnosis. Specific urine peptide patterns [5, 6] can be used for this purpose. In cases of glomerular, nephrotic, and non-selective proteinuria, membranoproliferative glomerulonephritis (MPGN/C3GP), focal segmental glomerulosclerosis (FSGS), minimal change disease (MCGN), membranous nephropathy (MN), or renal amyloidosis should be considered. Renal amyloidosis can be confirmed or ruled out by the ratio of lambda to kappa light chains. Membranous nephropathy (MN) can be detected by specific autoantibodies. If neither an abnormal light chain profile nor autoantibodies for MN are present, MCGN or FSGS are likely.

Inflammatory glomerulopathies are characterized by the excretion of erythrocytes in the urine. Further differentiation is possible through highly specific urine proteome patterns or genomic analyses. Alport syndrome can be diagnosed based on dysmorphic erythrocytes in the urine as well as by known mutations in the collagen IV gene. IgA nephropathy (IgAN), the most common glomerulonephritis worldwide, can be detected with high accuracy by the urine proteome pattern IgAN237 [7].

Rapid kidney failure, combined with proteinuria and dysmorphic erythrocytes in the urine, suggests disease of the entire glomerular compartment with extracapillary proliferation. Goodpasture syndrome can be diagnosed by detecting antibodies against the glomerular basement membrane. In autoimmune vasculitis, ANCA antibodies are indicative. Lupus nephritis can be diagnosed by detecting antinuclear and dsDNA antibodies.

Thanks to decades of research, it is now possible to assess the diagnostic reliability of biomarkers, genetic analyses, and proteomic patterns using existing histomorphological gold standards. The first steps toward a non-invasive "liquid kidney biopsy" have already been taken. This technology can already be used today and makes it possible to avoid a kidney biopsy and its associated risks.

c. Determination of medications

Based on the proteomic pattern in urine, it is possible to predict which medications or other therapeutic interventions (e.g., lifestyle changes, diet, etc.) the patient will respond to [8]. In this way, the optimal, personalized therapy can be determined for each patient.

The current diagnosable advanced state of the disease and the therapy that only then begins

Currently, chronic kidney disease (CKD) is usually diagnosed only when significant organ damage is already present. This is done either by measuring the glomerular filtration rate (GFR), which indicates a reduction in kidney function of more than 50%, or by detecting increased albumin excretion in the urine. Since 50% of patients with impaired renal filtration and significant kidney damage showed no abnormality in urinary albumin excretion (albumin is a very large protein), this parameter is unsuitable for detecting the early stages of the disease. This is the conclusion of the FDA, which, in its Letter of Support, advocates for proteomic analysis [2].

To accurately determine the underlying kidney disease, a kidney biopsy has often been performed. This involves taking a tissue sample from the kidney using a hollow needle, which is then examined by a specialist (pathologist). However, this procedure is highly invasive, carries significant risks, and is not suitable for all patients.

Conclusion

Proteomic analysis of urine represents a groundbreaking development in nephrology. It makes it possible to detect CKD at an early stage, prevent organ failure, and tailor treatment to the individual patient. This can not only prevent the need for dialysis or transplantation in many cases, but also significantly improve the life expectancy and quality of life of those affected.

Tumor diseases

Cancer can occur in various organs of the body and originates from different cell types. Most cancers begin on the internal and external surfaces of the body.

Prostate cancer

Prostate cancer (PCa) is the most common type of cancer in men in Germany [9]. The number of new cases of prostate cancer in 2022 was approximately 74,895. Prostate cancer rarely occurs before the age of 50. In older men, PCa is found in the majority of patients, but in most cases it is of low malignancy [2].

The PSA test is the most commonly used test for prostate cancer screening. The PSA test measures prostate-specific antigen. It is not a specific biomarker for detecting prostate cancer. It is merely an indicator of changes in the prostate. These changes can have many causes unrelated to prostate cancer (see Figure 2).

Figure 2: Possible causes for an elevated PSA level.

Sources of error in the assessment of the PSA value [11]

• Intra-individual variations: PSA values can fluctuate by +/-15%.
• Measurement method: There are variations between laboratories (up to about 5%).
• Handling of samples: Proper handling is crucial, with specific stability periods for centrifuged samples.
• Urinary tract infection: Infections can cause very high PSA levels (>100ng/ml), which can take up to a year to normalize.
• Acute urinary retention: This condition moderately increases PSA levels.
• Biopsy: PSA tests should be postponed for at least one month after biopsies.
• Hypogonadism: PSA production depends on testosterone levels and affects PSA levels in men with low testosterone.
• The production of prostate-specific antigen is androgen-dependent, and 5α-reductase inhibitors (e.g., finasteride, dutasteride), used in benign prostatic hyperplasia, lower the PSA level by 50%.

The dilemma of prostate cancer diagnosis using PSA - the cause of unnecessary biopsies and over-treatment!

The only necessary corrective to the predominantly false suspicion of cancer based on elevated PSA levels is currently the invasive biopsy, which is associated with significant side effects. However, prostate biopsy results often yield false positives and false negatives, leading to overtreatment in many cases: 90% of all radical prostate treatments are unnecessary, resulting in significant limitations – incontinence/impotence – and furthermore, unnecessary risks. The results of the ProtecT study [12], which showed overtreatment in 90% of all treatments and biopsies, have led to a crisis of confidence among patients in medicine as a whole.

The probability of the biopsy needles missing the tumor is high. A higher number of biopsies – up to 12 needles can be inserted into the prostate instead of 6 – and repeat biopsies have been intended to compensate for this. However, the increased number of biopsies and repeat biopsies also exponentially increase the risks of inflammation, tumor metastasis, and thus health hazards in prostate cancer diagnostics.

Figure 3: Proposed decision tree for a non-invasive, biomarker-based diagnostic approach to prostate cancer (PCa). The figure shows the available diagnostic options. If a definitive diagnosis and a sufficiently reliable treatment recommendation cannot be derived, the invasive diagnostic approach via prostate biopsy remains the last option.

Before performing an invasive prostate biopsy in a patient with an elevated PSA level, other, non-invasive options should be considered (see Figure 3). This should increasingly be achieved using mpMRI and fusion biopsy. MRI has a pooled sensitivity of 91% and a pooled specificity of 37% for clinically significant cancer (ISUP ≥GG2) [11]. This means that 63% of patients who would undergo a biopsy would not have clinically significant cancer.

Another limitation of MRI is that 40–50% of men undergoing an MRI do not receive a clear indication of the presence of a significant tumor (PIRADS ≤3). Because the result is ambiguous and the risk of significant prostate cancer is only 6–16%, these patients are usually subjected to an invasive biopsy [11]. Health insurance companies generally do not cover the costs of the preceding MRI, which amount to approximately €1,000 (up to €2,000), only the invasive biopsy.

To correct PSA and MRI results, the EAU guidelines recommend risk stratification using alternative methods or biomarkers to avoid magnetic resonance imaging scans and biopsy procedures.

Proteomics analysis, with its scientific definition and identification, represents the current state of medical knowledge.

Why is this methodological approach so precise? Cells constantly need to renew themselves. Some do so quickly, others take weeks. If the signals for regeneration are faulty, unnecessary cells can form. If this is not compensated for by the body's comprehensive mechanisms, so-called malignant cells establish themselves. This is the basis for cancer development, the growth of which is furthered by inflammatory processes in the body, which can also be caused by the environment and a contaminated food chain. Since these cellular changes in the body are controlled exclusively by proteins, proteomic analysis is the first method capable of mapping these alterations. Confirmation in studies relies on the limitations of methodological approaches such as PSA and biopsy. It can be assumed that the accuracy of proteomic analysis is even qualitatively better than currently reported. According to the available studies, proteomic analysis is extremely useful both in its detection with a negative predictive value of 93-94% [13, 14, 15] and also in determining whether dangerous prostate cancer is present, and should be performed after an abnormal PSA finding before invasive diagnostics or therapies.

Conclusion

Proteomic analysis not only corrects the PSA test in its predominantly false-positive findings, but due to its scientific methodological approach, it is also able to detect previously undetected serious cancer findings.

References

1. https://innovation-radar.ec.europa.eu/innovation/58774
2. https://www.fda.gov/media/99837/download
3. UN-Resolution A/RES/66/2 (2011)
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