Letters to the Editor
In Reply
We thank our correspondents for contributing to the discussion of our summary of the S3 guidelines (Association of the Scientific Medical Societies in Germany (AWMF), 166–005). The words of both authors completely express our sentiments. von Ahsen points out the difficulty of deciding from which threshold value, erythrocyturia should undergo microscopy. Our review article, in which we explained in a compressed form the content of the guideline, does not do justice to the complexity of this question (1). I refer readers to the actual guideline, which the AWMF will publish online in the near future. Here, we wish to emphasize that it is not the absolute erythrocyte count in urine that is crucial as a means of early detection but their persistence:
Monitoring with urine dipsticks, for example, has proved to be effective if it is conducted three to five times over a period of three to six months. The diagnosis of persistence requires a positive result for microhematuria on the majority of the dipsticks (for example, two out of three). An isolated finding of persistent hematuria is sufficient as an early detection sign for identifying kidney disease in about one third of young affected patients. In more than 90% this is a type IV collagen disorder from the Alport spectrum, with variants in the COL4A3/4/5 genes (2), which explains our focus on this syndrome in Figure 1.
In clinical practice we suggest diagnosing the presence of persistent microhematuria first. If this persists then—independently of the laboratory guideline cited by von Ahsen (3)—it is not to be considered physiological for life until the opposite has been proved and should be evaluated according to our S3 guideline.
Hallman echoes our sentiments when he points out the paramount importance to undertake one’s own microscopy. Here too, let me quote from the S3 guideline, which is soon to appear online (strong recommendation 2.5 by strong consensus): “We recommend in persistent microhematuria to measure acanthocytes in the urine sediment. The detection software of automated laboratories is currently less suitable for this task than critical evaluation by the technical assistant or the doctor. The reasoning: confirmation of 5% of acanthocytes in the urine sediment hints at glomerular disease with a specificity of more than 90% (sensitivity 60%). Because of a lack of suitably programmed detection software, many automated laboratories do not identify acanthocytes in the urine sediment.” The guideline group at this point makes special mention of the fact that carrying out urine microscopy and detection of acanthocytes yourself is an inherent part of advanced pediatric nephrology and nephrology training.
Hallmann emphasizes this explicitly on the basis of his own experience.
As both contributions to the discussion reflect, the implementation of our S3 guideline has the potential to crucially improve patient care in the early detection of chronic kidney disease.
DOI: 10.3238/arztebl.m2024.0188
On behalf of the authors
Prof. Dr. med. Oliver Gross
Klinik für Nephrologie und Rheumatologie
Universitätsmedizin Göttingen
gross.oliver@med.uni-goettingen.de
Conflict of interest statement
The authors of all contributions declare that no conflicts of interest exist.
| 1. | Latta K, Boeckhaus J, Weinreich I, Borisch A, Müller D, Gross O: Clinical practice guideline: Microhematuria in children and young adults—evaluation for the early detection of kidney disease. Dtsch Arztebl Int 2024; 121: 461–6 VOLLTEXT CrossRef MEDLINE PubMed Central |
| 2. | Alge JL, Bekheirnia N, Willcockson AR, et al.: Variants in genes coding for collagen type IV α-chains are frequent causes of persistent, isolated hematuria during childhood. Pediatr Nephrol 2023; 38: 687–95 CrossRef MEDLINE |
| 3. | Kouri TT, Hofmann W, Falbo R., et al.: The EFLM European Urinalysis Guideline 2023. Clin Chem Lab Med 2024; 62: 1653–786 CrossRef MEDLINE |
