A new device for simple and accurate urinary pH testing by the Stone-former patient.
OBJECTIVE
Urinary pH is an important factor linked to renal stone disease and a useful marker in the treatment of urolithiasis. Although the gold standard for measuring urinary pH utilizes a glass electrode and a pH meter, at present dipstick testing is largely used to estimate urinary pH. However, the accuracy and precision of this method may be insufficient for making clinical decisions in patients with lithiasis. The aim of this study is to describe a new device for urinary pH testing.


METHODS
The device includes a pH sensor based on differential measurement of an ISFET-REFET pair. The drawbacks associated with this type of configuration, namely short lifetime and manual fabrication, have been overcome in the prototype. An automatic one point calibration is performed when turning on the system. Two buffer solutions were utilized to determine the intra- and inter-day precision of the device. The pH of 30 fresh human urine samples was measured using a pH-meter, a dipstick and the new electronic device.


RESULTS
In some cases, dipstick measurements differed from those of the pH meter by more than 0.40 units, a clinically relevant discrepancy, whereas none of the measurements made with the new electronic device differed from the results of the pH-meter by more than 0.1 pH units.


CONCLUSIONS
This new electronic device has the possibility to be used by stone-formers to control their urinary pH at home, increasing the tools available for stone prevention and prophylaxis.
Laboratory of Renal Lithiasis Research, Faculty of Sciences, University Institute of Health Sciences Research (IUNICS-IdISPa), University of Balearic Islands, Ctra. de Valldemossa, km 7.5, 07122 Palma de Mallorca, Spain.
Felix
F
Grases
Laboratory of Renal Lithiasis Research, Faculty of Sciences, University Institute of Health Sciences Research (IUNICS-IdISPa), University of Balearic Islands, Ctra. de Valldemossa, km 7.5, 07122 Palma de Mallorca, Spain.
Adrian
A
Rodriguez
Laboratory of Renal Lithiasis Research, Faculty of Sciences, University Institute of Health Sciences Research (IUNICS-IdISPa), University of Balearic Islands, Ctra. de Valldemossa, km 7.5, 07122 Palma de Mallorca, Spain.
Francisco
F
Berga
Laboratory of Renal Lithiasis Research, Faculty of Sciences, University Institute of Health Sciences Research (IUNICS-IdISPa), University of Balearic Islands, Ctra. de Valldemossa, km 7.5, 07122 Palma de Mallorca, Spain.
Antonia
A
Costa-Bauza
Laboratory of Renal Lithiasis Research, Faculty of Sciences, University Institute of Health Sciences Research (IUNICS-IdISPa), University of Balearic Islands, Ctra. de Valldemossa, km 7.5, 07122 Palma de Mallorca, Spain.
Rafael Maria
RM
Prieto
Instituto de Microelectrónica de Barcelona, IMB-CNM (CSIC), Campus UAB, E-08193 Cerdanyola, Spain.
Isabel
I
Burdallo
Instituto de Microelectrónica de Barcelona, IMB-CNM (CSIC), Campus UAB, E-08193 Cerdanyola, Spain.
Alfredo
A
Cadarso
Instituto de Microelectrónica de Barcelona, IMB-CNM (CSIC), Campus UAB, E-08193 Cerdanyola, Spain.
Cecilia
C
Jimenez-Jorquera
Instituto de Microelectrónica de Barcelona, IMB-CNM (CSIC), Campus UAB, E-08193 Cerdanyola, Spain.
Antonio
A
Baldi
Devicare, Av. Diagonal 327, C-2., E-08009 Barcelona, Spain.
Rosendo
R
Garganta
Renal lithiasis; Urinary pH; pH measurement; pH self-control