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 to support CKD management were combined to provide guidance for their application. The figure shows the available biomarkers and their potential applications for specific diseases. If this decision tree cannot provide a definitive diagnosis, additional biomarkers—particularly for rare diseases—should be considered depending on the clinical picture. If a definitive diagnosis and sufficiently reliable treatment recommendation cannot be derived, the invasive diagnostic approach using kidney biopsy remains the last option.

Acute kidney injury (AKI) caused by circulatory problems can usually be reliably diagnosed based on the clinical history. Characteristic imaging features also allow the diagnosis of autosomal dominant polycystic kidney disease (ADPKD) and obstructive kidney diseases, such as congenital malformations of the urogenital tract (CAKUT). In structural kidney diseases not caused by diabetes or hypertension, the next diagnostic step is the differential diagnosis of the disease. 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 glomerulonephritis (MCGN), membranous nephropathy (MN), or renal amyloidosis should be considered. Renal amyloidosis can be confirmed or ruled out by the lambda-to-kappa light chain ratio. 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 red blood cells in the urine. Further differentiation is possible using highly specific urine proteome patterns or genomic analyses. Alport syndrome can be diagnosed based on dysmorphic red blood cells in the urine and known mutations in the collagen IV gene. IgA nephropathy (IgAN), the most common glomerulonephritis worldwide, can be diagnosed with high accuracy using the urine proteome pattern IgAN237 [7].

Rapid loss of renal function, 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. ANCA antibodies are a key marker for autoimmune vasculitis. Lupus nephritis can be diagnosed by detecting antinuclear and dsDNA antibodies.

Thanks to decades of research, it is now possible to evaluate the diagnostic reliability of biomarkers, genetic analyses, and proteomic patterns using the current 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 medication

Based on the proteome 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]. This allows the optimal, personalized therapy to be determined for each patient.

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

Currently, CKD is usually only diagnosed when significant organ damage has already occurred. This is done either based on the glomerular filtration rate (GFR), which indicates a reduction in kidney function of more than 50%, or by detecting elevated albumin excretion in the urine. Since 50% of patients with impaired renal filtration, i.e., significant kidney damage, showed no abnormalities in albumin excretion in the urine (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 advocates proteomic analysis in its "Letter of Support" [2].

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

Conclusion

Urine proteomic analysis represents a groundbreaking development in nephrology. It enables early detection of CKD, prevention of organ failure, and individualized treatment. This not only prevents the need for dialysis or transplantation in many cases, but also significantly improves the life expectancy and quality of life of those affected.

Tumor diseases

Cancer can occur in a wide variety of organs throughout the body and originates from various cell types. Most cancers originate from the internal and external surfaces of the body.

Prostate cancer

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

The PSA test is the most commonly used test for screening for PCa. The PSA test is a prostate-specific antigen. It is not a specific biomarker for detecting prostate cancer. It is merely an indication of changes in the prostate. This can have many causes that have nothing to do with prostate cancer (see Figure 2).

Figure 2: Possible causes of an elevated PSA level.

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

• Intra-individual variations: PSA values can fluctuate by +/-15%
• Measurement method: There are deviations between laboratories (up to about 5%).
• Sample handling: Proper handling is critical, 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 testing 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 levels.
• The production of prostate-specific antigen is androgen-dependent, and 5α-reductase inhibitors (e.g., finasteride, dutasteride), which are used for benign prostatic hyperplasia, reduce PSA levels 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 has so far been an invasive biopsy, which is associated with significant side effects. However, prostate biopsy results often yield false-positive and false-negative results, which in many cases lead to overtreatment: 90% of all radical prostate treatments are unnecessary, resulting in significant limitations—incontinence/impotence—and, in addition, unnecessary risks. The results of the ProtecT study [12], which showed overtreatment of 90% of all treatments and biopsies, have led to a crisis of patient confidence in medicine as a whole.

The probability of biopsy needles missing the tumor is high. A higher number of cores—12 needles can be inserted into the prostate instead of 6—and repeat biopsies have previously been used to compensate for this. At the same time, the higher number of cores and repeat biopsies exponentially increase the risk of inflammation, tumor spread, and thus the health risks associated with prostate cancer diagnosis.

Figure 3: Proposed decision tree for a non-invasive, biomarker-based diagnostic approach in prostate cancer (PCa). The figure shows the available diagnostic options. If a definitive diagnosis and sufficiently reliable treatment recommendation cannot be derived, the invasive diagnostic approach using 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 addressed with mpMRI and fusion biopsy. MRI has a pooled sensitivity of 91% and a pooled specificity of 37% for significant cancer (ISUP ≥GG2) [11]. This means that 63% of patients who would undergo a biopsy do not have significant cancer.

Another limitation of MRI is that 40–50% of men undergoing MRI do not receive a clear diagnosis regarding the presence of a significant tumor (PIRADS ≤3). Because the result is inconclusive and the risk of significant PCa is only 6–16%, these patients typically undergo invasive biopsy [11]. Health insurance companies generally do not cover the approximately €1,000 (up to €2,000) cost of the preliminary MRI, 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.

Proteome analysis, with its scientific definition and recognition, represents the current state of medical knowledge.

Why is this methodological approach so precise? Cells must constantly renew themselves. Some do this in a short time, others take weeks. If the signals for regeneration are faulty, cells that are no longer needed can form. If this is not compensated for by the body's comprehensive mechanisms, so-called degenerated cells establish themselves. This is the basis for the development of cancer, whose growth is further promoted by inflammatory processes in the body, which can also be caused by the environment and a polluted food chain. Since these cellular changes in the body are controlled exclusively by proteins, proteomic analysis is the first to be able to depict these changes. Confirmation in the studies is based on inadequate methodological approaches such as PSA and biopsy. It can be assumed that the accuracy of proteomic analysis is qualitatively better than stated. According to the available studies, proteomic analysis is extremely useful both in its detection with the negative predictive value of 93-94% [13, 14, 15] and also in determining whether dangerous prostate cancer is present, after abnormal PSA findings 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, 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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