[Whole PTH and 1-84/84 PTH ratio for the non invasive determination of low bone turnover in renal osteodysthrophy]. / Utilidad de la determinación de PTH entera y del cociente PTH 1-84/7-84 en el diagnóstico no invasivo de osteodistrofia de bajo recambio.

The conventional intact PTH assays detect not only PTH 1-84 but also inactive fragments (as PTH 7-84) that accumulate in renal failure. There has been a recent development of a new PTH assay that measures only true 1-84 PTH (Whole PTH or CAP assay, Scantibodies). As 7-84 PTH fragment is antagonistic on bone effects of 1-84 PTH, Moniere-Faugere has suggested that 1-84/7-84 PTH ratio less than 1 is predictive of low turnover. We evaluated the usefulness of CAP assay and the 1-84/7-84 PTH ratio as markers of bone turnover in a groups of 24 patients in peritoneal dialysis (PD). Patients were classified as having low bone turn over if they had a Total PTH (similar to intact PTH) of less than 100 pg/ml. We also measured serum CrossLaps (CTX) as another serum resorption marker. Patients had a mean Whole PTH of 95.5 pg/ml and a mesan total PTH of 155.4 pg/l (range 9 to 900). Whole PTH represented 69.1% of total PTH. Fifteen patients (62.5%) had a total PTH of less than 100. These patients had a 1-84/7-84 relationship of 1.9 +/- 1.8 while 9 patients with Total PTH more than 100 had a relationship of 1.29 +/- 0.6 (p = NS). There was a tight correlation between Whole PTH and total PTH (r = 0.98; p < 0.0001) and with serum CTX (r = 0.78; p < 0.0001). We conclude that 1-84/7-84 ratio does not seem useful in the prediction of low bone turnover and that Whole PTH does not seem to be more useful than intact PTH in the prediction of bone turnover in this population. Future studies should correlate this markers with direct measurements of bone turnover in bone biopsies to demonstrate their usefulness in the prediction of the type of renal osteodystrophy.

Utilidad de la determinación de PTH entera y del cociente PTH 1-84/7-84 en el diagnóstico no invasivo de osteodistrofia de bajo recambio / Whole PTH and 1-84/7-84 PTH ratio for the non invasive determination of low bone turnover in renal osteodystrophy

Los ensayos convencionales de PTH intacta detectan tanto la PTH 1-84 como fragmentos inactivos (como la PTH 7-84) que se acumula en insuficiencia renal. Recientemente se ha desarrollado un nuevo ensayo de PTH que mide solo la verdadera PTH 1-84 (PTH entera, Whole PTH o CAP assay, Scantibodies). Como el fragmento PTH 7-84 es antagónico sobre los efectos óseos de la PTH 1-84, Moniere-Faugere han sugerido que un cociente PTH 1-84/7-84 menor a 1 podría predecir bajo recambio óseo. Nosotros evaluamos la utilidad del ensayo de PTH entera y de la relación PTH 1-84/7-84 como marcadores de recambio óseo en un grupo de 24 pacientes en diálisis peritoneal (DP). Los pacientes se clasificaron como que presentaban bajo recambio óseo si tenían una PTH total (ensayo similar a la PTH intacta) de menos de 100 pg/ml. También medimos los Crosslaps (CTX) séricos como otro marcador de resorción. Los pacientes tuvieron una media de PTH entera de 95,5 pg/ml y una media de PTH total de 155,4 pg/ml (rango 9 a 900). La PTH entera representó el 69,1% de la PTH total. Quince pacientes (62,5%) tuvieron una PTH total menor a 100. Estos pacientes tuvieron cociente PTH 1-84/7-84 de 1,9 ± 1,8 mientras que 9 pacientes con una PTH total mayor a 100 tuvieron un cociente de 1,29 ± 0,6 (p = NS). Hubo una estrecha correlación entre PTH entera y PTH total 9 r = 0,98; p < 0,0001) y con los CTX séricos (r = 0,78; p < 0,0001). Nosotros concluimos que el cociente 1-84/7-84 no parece ser útil en la predicción bajo recambio óseo y que la PTH total no parece ser más útil que la PTH intacta en la predicción del recambio óseo en esta población. Futuros estudios deberán correlacionar estos marcadores con mediciones directas del recambio óseo en biopsias óseas para demostrar su utilidad en la predicción del tipo de osteodistrofia renal

The conventional intact PTH assays detect not only PTH 1-84 but also inactive fragments (as PTH 7-84) that accumulate in renal failure. There has been a recent development of a new PTH assay that measures only true 1-84 PTH (Whole PTH or CAP assay, Scantibodies). As 7-84 PTH fragment is antagonistic on bone effects of 1-84 PTH, Moniere-Faugere has suggested that 1-84/7-84 PTH ratio less than 1 is predictive of low turnover. We evaluated the usefulness of CAP assay and the 1-84/7-84 PTH ratio as markers of bone turnover in a groups of 24 patients in peritoneal dialysis (PD). Patients were classified as having low bone turn over if they had a Total PTH (similar to intact PTH) of less than 100 pg/ml. We also measured serum CrossLaps (CTX) as another serum resorption marker. Patients had a mean Whole PTH of 95.5 pg/ml and a mesan total PTH of 155.4 pg/l (range 9 to 900). Whole PTH represented 69.1% of total PTH. Fifteen patients (62.5%) had a total PTH of less than 100. These patients had a 1-84/7-84 relationship of 1.9 ± 1.8 while 9 patients with Total PTH more than 100 had a relationship of 1.29 ± 0.6 (p = NS). There was a tight correlation between Whole PTH and total PTH ( r = 0.98; p < 0.0001) and with serum CTX ( r = 0,78; p < 0,0001). We conclude that 1-84/7-84 ratio does not seem useful in the prediction of low bone turnover and that Whole PTH does not seem to be more useful than intact PTH in the prediction of bone turnover in this population. Future studies should correlate this markers with direct measurements of bone turnover in bone biosies to demonstrate their usefulness in the prediction of the type of renal osteodystrophy

Estimación de la prevalencia de osteodistrofia renal de bajo recambio a través de marcadores bioquímicos en una población en diálisis peritoneal / Estimation of the prevalence of adynamic bone disease using biochemical markers

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