Pilocarpine Iontophoresis Test Research Articles

A case of congenital insensitivity to pain with anhidrosis.

A case of congenital insensitivity to pain with anhidrosis.

Hyperchlorhidrosis Caused by Homozygous Mutation in CA12, Encoding Carbonic Anhydrase XII

Excessive chloride secretion in sweat (hyperchlorhidrosis), leading to a positive sweat test, is most commonly indicative of cystic fibrosis yet is found also in conjunction with various metabolic, endocrine, and dermatological disorders. There is conflicting evidence regarding the existence of autosomal-recessive hyperchlorhidrosis. We now describe a consanguineous Israeli Bedouin kindred with autosomal-recessive hyperchlohidrosis whose sole symptoms are visible salt precipitates after sweating, a preponderance to hyponatremic dehydration, and poor feeding and slow weight gain at infancy. Through genome-wide linkage analysis, we demonstrate that the phenotype is due to a homozygous mutation in CA12, encoding carbonic anhydrase XII. The mutant (c.427G>A [p.Glu143Lys]) protein showed 71% activity of the wild-type enzyme for catalyzing the CO₂ hydration to bicarbonate and H(+), and it bound the clinically used sulfonamide inhibitor acetazolamide with high affinity (K(I) of 10 nM). Unlike the wild-type enzyme, which is not inhibited by chloride, bromide, or iodide (K(I)s of 73-215 mM), the mutant is inhibited in the submicromolar range by these anions (K(I)s of 0.37-0.73 mM).

The evaluation of a novel conductometric device for the diagnosis of cystic fibrosis

We evaluated the diagnostic discrimination of a new micro-flow cell device (Nanoduct) which measures sweat conductivity in situ at a regional referral centre for cystic fibrosis (CF). The device was evaluated in comparison to the measurement of sweat chloride with the established quantitative pilocarpine iontophoresis test (QPIT) and extended in a number of patients to conductivity measurements in liquid sweat collected with the Macroduct system. Sweat testing was conducted simultaneously on patients referred for diagnostic sweat testing, on patients known to have CF and on adult volunteers. The intra-individual variability, the failure rate and diagnostic accuracy were determined. A total of 110 tests were performed on 100 individuals, 36 of whom had classical CF and six of whom had non-classical CF. The Nanoduct system produced a false negative result in one quarter of the patients with classical CF. Moreover, conductivity was negatively biased compared with chloride in this group. Repeat testing of the false negatives using a new batch of sensors and/or measuring conductivity in liquid sweat collected with the Macroduct device gave accurate diagnostic discrimination indicating that the original sensors were faulty. Photographic examination confirmed that a batch of sensors were defective. Our experience suggests that the prototype microflow cell conductometric device cannot be used for the diagnosis of CF due to the high false negative rate. As a consequence of this study, the manufacturers have implemented a pre-testing system to quality control the sensors prior to issue.

Cystic Fibrosis in Korean Children: A Case Report Identified by a Quantitative Pilocarpine Iontophoresis Sweat Test and Genetic Analysis

Cystic fibrosis (CF) is inherited as an autosomal recessive trait, and the mutations in cystic fibrosis transmembrane conductance regulator (CFTR) gene contributes to the CF syndrome. Although CF is common in Caucasians, it is known to be rare in Asians. Recently, we experienced two cases of CF in Korean children. The patients were girls with chronic productive cough since early infancy. Chest computed tomography showed the diffuse bronchiectasis in both lungs, and their diagnosis was confirmed by the repeated analysis of a quantitative pilocarpine iontophoresis test (QPIT). The sweat chloride concentrations of the first patient were 108.1 mM/L and 96.7 mM/L. The genetic analysis revealed that she was the compound heterozygote of Q1291X and IVS8 T5-M470V. In the second case, the sweat chloride concentrations were 95.0 mM/L and 77.5 mM/L. Although we performed a comprehensive search for the coding regions and exon-intron splicing junctions of CFTR gene, no obvious disease-related mutations were detected in the second case. To our knowledge, this is the first report of CF in Korean children identified by a QPIT and genetic analysis. The possibility of CF should be suspected in those patients with chronic respiratory symptoms even in Korea.

Buccal cell DNA mutation analysis for diagnosis of cystic fibrosis in newborns and infants inaccessible to sweat chloride measurement.

To assess the application of DNA-based cystic fibrosis transmembrane conductance regulator (CFTR) gene mutation analysis as a primary cystic fibrosis (CF) diagnostic test in preterm and term newborns and infants for whom the quantitative pilocarpine iontophoresis test (QPIT) cannot be used. Retrospective survey. DNA Diagnostic Laboratory, Children's Hospital, Boston, Massachusetts. Buccal cell DNA samples were received from inpatients, outpatients, and three neonatal intensive care units. Detection of at least 1 of 12 CFTR mutations. Between November 1, 1992, and April 30, 1994, 28 newborns and infants under 12 months of age at risk for CF had CFTR DNA mutation analysis performed because a sweat chloride (SC) value could not be obtained. QPIT was either not performed (infant weight <2 kg, QPIT not available at site of hospitalization, or infant not accessible to QPIT laboratory) or was inconclusive (sweat volume <75 mg or indeterminate SC [>/=40, <60 mEq/L]). The postnatal age at time of testing ranged from 1 day to 11 months, and gestational age at birth from 25 to 40 weeks. Six (21%) of 28 infants with unobtainable or indeterminate QPIT had 1 or 2 CFTR mutations detected. Immediate CF diagnosis by direct detection of 2 CFTR mutations was made in 5 of these 6 patients. Definitive CF diagnosis in the infant with 1 CFTR mutation was delayed until an elevation in SC could be documented. The patients with no CFTR mutations detected had a low likelihood of CF. For infants in whom CF is suspected but QPIT cannot be obtained, buccal cell DNA-based CFTR mutation analysis can be used as a rapid, noninvasive primary diagnostic test. This simple mode of DNA collection may aid in the diagnosis of other inherited disorders in newborns.

Clinical evaluation of the macroduct sweat collection system and conductivity analyzer in the diagnosis of cystic fibrosis

The purposes of this study were to compare sweat tests used in diagnosing cystic fibrosis (CF), as performed with the Macroduct collection system, with those utilizing the more laborious quantitative pilocarpine iontophoresis test (QPIT), and to ascertain the efficacy of the Sweat-Chek conductivity analyzer in eliminating some possibly unnecessary chloride analyses. A Macroduct sweat test was performed on one arm and a QPIT on the other on 1090 patients, 93 of whom had CF. Of these, 514 patients (43 with CF) also had a conductivity determination on the Macroduct sweat sample. All subjects were referred to the laboratory of one of us (K.B.H.) for sweat testing. Of the QPIT samples, 0.7% were inadequate, as were 6.1% of those from the Macroduct system. When sodium and chloride concentrations from the two tests were compared, the standard errors of the estimate were 3.90 and 3.85, respectively. Agreement within 8 mEq/L could then be expected with 95% confidence limits. With use of the Sweat-Chek analyzer, no patient with CF was found to have a conductivity of less than 90 mmol/L, whereas 430 (91%) of the non-CF subjects had a conductivity of less than 50 mmol/L. None of those 430 subjects had a sweat chloride value > 32 mmol/L. We conclude that the Macroduct collection system provides results equally as satisfactory as those provided by the QPIT and that the Sweat-Chek analyzer frequently eliminates the necessity of measuring chloride concentrations. (J P EDIATR 1994;124:255-60.)

Cystic Fibrosis Gene Mutation in Two Sisters with Mild Disease and Normal Sweat Electrolyte Levels

CYSTIC fibrosis is the most common fatal recessive disease in whites. In the past the diagnosis has been based on the presence of lung disease, pancreatic exocrine insufficiency, and increased sweat electrolyte concentrations.1 Patients with cystic fibrosis have well-defined abnormalities in epithelial tissue, including defective cyclic AMP—mediated regulation of chloride channels and an increased transepithelial potential difference, which reflects increased sodium absorption and decreased chloride permeability.2 3 4 5 6 The raised sweat chloride values that result from impaired reabsorption of salt in the sweat ducts have been exploited in the pilocarpine iontophoresis test, the cornerstone of diagnosis since 1959.7 Although the vast majority . . .

Influence of sex and growth hormone deficiency on sweating

Sweat secretion rate (SSR) was measured by the pilocarpine iontophoresis test in (a) 254 healthy children and adolescents (aged 6.0 to 19.2 years, mean age 11.2 years); in (b) 58 healthy adults (aged 20.4 to 75.2 years, mean age 37.6 years); and in (c) eight prepubertal patients with growth hormone (GH) deficiency (aged 4.2 to 13.5 years, mean age 8.9 years). Boys had higher median values for SSR than girls (pre-pubertal children: 92.7 vs 64.5 mg 30 min-1 pubertal children: 110.3 vs 73.1 mg 30 min-1), and men showed higher values than women (135.5 vs 49.2 mg 30 min-1). In addition, the change in sweat excretion rate from childhood to adulthood showed a difference between the sexes. Both pre-pubertal and pubertal boys had a lower secretion value than adult men (p less than 0.001 and 0.01, respectively), whereas girls showed higher secretion values than adult women (p less than 0.01 and p less than 0.001, respectively). There was a significant increase in SSR from prepuberty to puberty (p less than 0.001) for both sexes. The children with GH deficiency, all pre-pubertal, showed significantly reduced SSR (p less than 0.001) compared with the healthy children (median values: 32.8 vs 80.0 mg 30 min-1). We conclude that (a) sweat secretion pattern in children shows a significant sex difference and (b) sweating in children is dependent on growth hormone.

Reappraisal of the chloride plate test as screening test for cystic fibrosis.

A rapid and simple screening test for detecting cystic fibrosis, described in 1956, has been used routinely for 21 years; the results during a 15-month period are compared with those using the quantitative pilocarpine iontophoresis sweat test. In the chloride agar plate test the concentration of chloride on the finger tips is evaluated accordingly to the intensity of the imprint. Readings of 2+ or less excluded cystic fibrosis in 1589 cases with only two doubtful instances, whereas 4+ readings were recorded in 198 cases of cystic fibrosis and 3+ readings in 15 cases of cystic fibrosis. In doubtful cases 4 individuals had 4+ readings and 11 had 3+ readings. This screening test does not replace the quantitative pilocarpine iontophoresis test but it does identify an individual who is likely to have the disease and who requires further tests. It is not reliable for infants aged under 2 months.