Experience
and Reason
Briefly
Recorded
:‘.Iii \I((hicill(’ one nmtist pa’ attention imot to 1)lausible theorizing l)tIt to experi(nc( tIm(l reason together. . . . I agree that theorizing is to be approved, prsi(le(l timat it is based on facts, amid
systematically nmake its deductions from what is observed. . . . But conclusions drawim from
unaided reason can hardly i)e serviceable; only timose drawn from observed fact.” I hippocrates:
Precepts.
are published here. Comments and critici.sms
2.
14720
3.
4.
6.
261
PEDIATRICS, Vol. :36, No. 2, August 1965
(Short comm ii nication.s of factual materwi app(’ar (IS Letters to the Editor.)
The
Silver
Electrode
Method
for
Rapid
Analysis
of
Sweat
Chloride
A new sweat test which uses a standard
thermal stiniulus and a silver electrode
per-mits (1nantitatiye analysis of the chlorkie
eon-tdlit of hunian sweat in less than 6 minutes.
The test can be done on over 100 individuals
iii less than 1 hour’s time.
EQUIPMENT
1. Beckman Model 76 expanded scale pH
millivolt nieter
2. Silver Billet combination electrode
Beck-maim H39187
3. Therniostatic temperature controlled
\vater IXith
4. One 1)h1h1d ahmniintiiii cylinder (6.2 cm
(lianleter, 5 cni height)
5. Temp-block heater
EXPENDABLE MATERIALS
KC1 AgCl Solution Beckman No. 14620
10% NH1NO Solution Beckman No.
Saturated KCI Solution
NaCI, Reagent grade ACS
Distilled water
10 X 10 cm gauze squares
10 X 10 cm parafilm squares
PREPARATION OF THE ELECTRODE (see Fig. 1)
The billet of time silver billet combination
electrode is electroplated according to time
manufacturer’s directions. When adequately
coated with AgCl the billet turns violet. A
rubber protector cap is placed over the end
of the electrode Past the linen fibers to
pro-tect the electrode when it is not in use.
A 1.4 cm hole is (lulled Iii the center of
the plastic cap from a 10 ml (liSpoSai)le
sy-ringe. This hole will allow the cai to slide
freely over tile electrode. An a(lditional rui)l)er
sleeve, similar to those already on the
dee-trode, is 1)lmtce(l around the i)illet of the
dcc-trode ai)OUt 2 mimi above time linen fibers. The
I)llstic cap is Sli)ped down over the rubi)er sleeve, wedged into 1ice so that the edge
of time open end is even with the linen fibers. The plastic cal) keeps time electrode
perpemi-dicular to the skimi surface, minimizes time e’a1)oration of sweat while the test is l)emg
nm, protects time eim(l of time electrode from
injury 1il(l niakes it easy to hold the electrode
on tile skin with a constant pressure.
Time upper chamber is filled vith saturated
KCI AgCl solution (Beckman No. 14620) and time hole is covered with the rui)ber sleeve.
Time lower cimamber of time combination
dcc-trode is filled with 10% NII,NO solutiomm
(Beck-man No. 14720). This solution serves as a
i)ri(lge i)etween the reference solutiomi jim tile upper chamber and time sample. The 10%
NH,NO is changed eriiitiiy to prevent
commtamination of time sample with Ci ions froimi
time reference solution. More stable readings
are obtained when the lower chamber filling
hole is imot covered.
STANDARDIZATION AND ZEROING
Distilled water and staimdard solutiomms of
5 aimd 100 immEq I NaCI are placed immcovered
test tubes and warmed to 37#{176}C usiimg tile
262 SWEAT CHLORIDE ANALYSIS
Fir;. 1. Silver billet combination electrode
Beck-man No. 1139187 with insert diagram of syringe cap modification which permits in situ analysis
of sweat chloride.
The pH meter is turned on for 20 to 30
minutes warm-lip. The silver billet is then
immersed ill the warmed 5 mEq/i solution.
The asymmetrY control dial is used to select
a stable reading on the low end of the scale.
When this reading is recorded, the pH meter
is placed on standby, and the electrode tip is
rinsed off with distilled water and dried by
touching with a 10
x
10 cm gauze square. The electrode is then placed in the 100 mEq/l Cl solution and the reading recorded. For accurate measurement there should be adiffer-ence of 7 to 8 scale units from the 5 mEq/l
solution to the 100 mEq/l solution. If the
differences are less than 6 units the electrode
may need to be recoated with silver, the upper
and lower chamber solutions may need to be changed, the solutions being measured may be
grounded, or the meter may have had
in-sufficient warm-up.
The results are plotted on semi-logarithmic
two-cycle graph ptper with millivolt scale
readiimgs along the abscissa, and chloride
con-centrations of the standard solutions along the
ordiimate. A straight limme is drawn between the
and 100 mEq/1 results. This is the reference
line from which chloride concentrations are
determined Oil future uimknown specimens. It
is necessary to restandardize the meter eacim
day or whenever it is uimplugged or moved.
Sometimes tile p’ meter Imas a tendency to
drift and the standardization must be checked
every 10 or 20 unknowim dleterrninat!ons. This can be clone in less than a minute if the
stami-clards are kept warm in the temp-block heater.
READING OF UNKNOWN
The volar surface of the forearm is time
lIre-ferred test location, but with care other areas
may also be used. The selected area is washed
vith distilled svater 1111(1 thorougimly dried svith gaumze. The ahuiimiimumm cylinder, 1)reheated to
48#{176}Cin the water bath, is dried and one end
is covered with parafilm. Tue parafllm-covered
side is held firmly on the washed and dried
area for 5 minutes. The parafllm is an inert
barrier to the sweat and prevents
contamina-tion of the sweat with surface ions from the
aluminum cylinder. Once the heated cylinder
is placed on the skin it is not removed during
the 5 minutes heating because the sweat will
evaporate rapidly from the heated surface, and
an abnormally high reading will occur.
At the end of 5 minutes the heated cylinder
is removed. The mean skin temiiperature is
36.7#{176}C with a range from 36.1#{176}to 37.2#{176}C.
The rinsed audi blotted ti}) of time silver
elec-trode is immediately placed1 011 the nmoist skin surface. The skin and subcutaneous tissue of
the volar surface of the forearm are pushed
up on both sides of the electrode to fornl a flat
or concave surface SO that the electrode tip
can sink into time skin and the plastic shield
cami form an airtight seal. Tile electrode is
held with a firm but not hard pressure. A
stable reading is obtained in 10 to 20 seconds.
If the electrode is kept in plmce for a long
tinie time scale readiimg vili gra(luallv cimange
because of evaparation aimd coimcentratiimg of
the iOIlS. This technique is ac(1uired b
tice.
If the needle fails to reach a Stli)le 1)DSit’d)il
there are several other likely reasons. A very
high millivolt reading imidicates insufficient
sweating. A vemy low reading indicates
ground-ing of the electrode caused by the pitieiit
touching the meter or SOlid coimductor. Aim
unstable readiimgmay be time result of excessive
pressure which squeezes the moisture from
under the silver billet or of tilting which
sil-Sweat Chloride, Meq’s/L
by Silver Electrode
Sweat Test #{149}
A
.. Sweat Chloride, Meq’s/L
‘S. #{149}#{149}#{149} by Pilocarpine lontophoresis
:‘::#{149}.
.. Sweat TestEXPERIENCE AND REASON-BRIEFLY RECORDED
TABLE I
263
(‘osii’.siusox 01’ IEAN, SrrAN[)Aiii) I)F:sI.uTI0N ANt) ltAN(;E OF SWEAT CumoumoF: VAiIS FIIOM PATIENTS iSITH (‘isTie F’iimuosis ANt) (‘oNTimoi PATIENTS Owr.sINED BY hEATED ALIMINIM (‘YIIN’ni.:m(-SiivF:It ELECTRODE AND
Pi i0(AR1INE IoNroI’iIouESis-( ‘oLrLovE (iitoutoosi ETEII EAT TESTS
(‘witrols Patients wit/i (‘ystic Fibrosis
No. Mean S.D. Range No. Mean S.D. Range
Silverelectrode 8 13.0 6.5 5-30 49 89.2 18.6 55-130
Pilocarpine 11.0 5.8 3-’25 49 95.1 14.6 70-130
ver i)illet. A high or unstable reading Iiiay
occur if time linen fibers have beeim dried by
excessive blotting with a dry gauze square.
Surface moisture n the silver billet is best
removed with a gauze square just damp with
distilled water. A rerun of the test is indicated
wimenever tilere is a spurious reading or a
reading ai)ove the normal range. 1v\Then a
definitely high reading is established with the
silver electrode a routme pilocarpine
ionto-1)hore.sis-Coitiove chloridometer sweat test is
done to (OtifilTfl the observation.
RESULTS
The heated alurninumii cylinder-silver
elec-trode test ssas compared to the pilocarpine
iontophoresis-Coltlove chloridometer sweat test
of Gibsoll and Cook.1 These data are
sum-marized in Table I and depicted in Figure 2.
The correlation coefficient for these two
meth-ods is 0.935. This is highly significamlt with a t
value )robability of chance occurrence of 0.001.
COMMENT
iliese data are siinilar-tlme correlation
co-efficient is very imigim aimd the slope of the
regression equatioim is imear come-but they are
not i(lentical. Since the accuracy of the silver
electrode approaches that of the Coltiove
cimloridonieter, the niost likely explanation for
the discrepaiicy is that the sweat tested differs
for each method. This difference may be in
the iimtensity of the stimulus to sweat or iii
the (luration of sweat collection.
Piiocarpine stimulation is known to pro(luce
(1 rapid rate of sweatiimg.2 The rate of
sweat-ing iim(luced l)y time heated aiuniinum 1)lock
is unknown i)llt the observed higher
concert-tratioim of chloride fl the control patients and tue lower concentration of chloride in patients
with cystic fibrosis may reflect differences in
capacity to respond to chemical and thermal
i-(luction. Tile duration of sweat collection
may also be important. Time sweat produced
in the first minutes of timermal stimulatioim has
a lower concentratioim of chloride than sweat
produced after prolonged heating.3 This may
also be true for the early and late sweat
in-duced by chemical stimulus.
This new sweat test may have wide
ap-plication i)ecauSe it is rapid, quammtitative, ammd
inexpemisive wheii large miumbers of tests are
done. Large populations can 1)e screened for
cystic fibrosis. We have tested a total of 1,324
children in three school systems in less timaim
12 hours time. Quantitative data are being
gathered on children of different racial origin.
Newborn infants are being tested for cystic
fibrosis. Over 90% of newborn infants can be
successfully tested with this technique by 3
days of life. It is hoped that this test will
Permit early diagnosis of cystic fibrosis so
-J
5)
40
20
00
80
60
40
20
“020 40 60 80 100 120 140
Meq/L
Fic. 2. Correlation diagram of silver electrode and
i)iloc1rPitie ioimtoi)horesis sweat cimloride values oh-tamed simultaneously from normal children and
children with cystic fibrosis. The equation for the least squares regression line is: Y = 4.5 + 0.86
264 INTRAUTERINE RUBELLA
the prophylactic treatment can be started
be-fore I)ril11iiiarY’ complications develop.
SUMMARY
The silver electrode sweat test 1)rovidles
quantitative sweat chloride values comparable
to values obtained with the standard
pilocar-pine iontophoresis method of Cibson and
Cooke. The silver electrode sweat test is faster.
WARREN
J.
WARWICK, M.D.USPHS Research Career Development Awardee 5K3-A1-14035-04
LELAND HANSEN, BA., Junior Scientist
Department of Pediatrics
University of Minnesota Medical
Center
Minneapolis, Minnesota 55455
This study has been supported by a Cystic
Fi-brosis Care, Research and Teaching Center grant
from the National Cystic Fibrosis Research
Foun-dation and a grant in aid from the Minnesota
Cystic Fibrosis Chapter.
REFERENCES
1. Gibson, L. E., and Cooke, R. E.: A test for
concentration of electrolytes in sweat in
cystic fibrosis of the pancreas utilizing
pilo-carpine by iontophoresis. PEDIATRICS, 23:
545, 1959.
2. Cibson, L. E., and di Sant’ Agnese, P. A.:
Studies of salt excretion in sweat:
Relation-ships between rate, conductivity and
electro-lvte composition of sweat from patients with
cystic fibrosis and from control subjects. J.
Pediat., 62:855, 1963.
3. Berenson, G. S., and Burch, C. E. : A study of
the sodium, potassium, and chloride con-tents of thermal sweat of man collected
from small isolated areas of skin. J. Lab.
Cliii. Med., 42:58, 1953.
Generalized
Bone
Changes
and
Thrombocytopenic
Purpura
in
Association
with
lntra.
uterine
Rubella
Changes in the bones in association with intrauteriime rubella have not been reported
previously. We wish to describe this
associ-ati()ii in two newborn infants with
thrombocy-topenic psirpuira. The infants were delivered
of mothers with a history of rubella in the
first trimester of pregnancy. In both instances the infants were found to harbor an
interfer-ing agent with the characteristics of the
ni-l)ella virus in tissue culture. It is hopedi that
this report svill prompt llySiti1ii5 to look for
these boime chailges in otimer iimfants borim
with intrauterine nmbella infection.
CASE 1
A girl of Puerto Rican extraction weighing
2,380 gnm was delivered at the City Hospital
Ccii-ter at Elmhurst on October 9, 1964, after a
40-week gestation. The mother had exl)erienced a
mild illness with fever and a rash diagnosed h
her family physician as rubella 58 days after the
onset of her last menstrual period. On the c1a the
rash appeared she received 12.5 ml of
gamma-globulin. Additional l)re1matul medications included vitamin supplementatioim throughout pregnancy,
small (luantities of aspirimm at the time of the
exan-them, and parenteral meperidine hydrochloride,
30 mg, promazine hydrochloride, 15 mg, and
sco-polamine hydrochloride, 0.4 mg, 30 minutes prior
to delivery. At birth the infant received
intramus-cular aqueous penicillin C, 50,000 units, as
rou-tine gonococcal ophthalmia prophvlaxis, and
in-tramuscular plivtonadione, 1 mg.
Within an hour after birth, a generalized
svm-metrical purpuric eruption was observed, time
Ic-sions measuring up to 0.5 cm in diameter.
Physi-cal examination was otherwise unremarkable. No
further hemorrhagic manifestations occurred, the
original purpura disappearing b the sixtim clas’.
jaundice was never evident.
During the first day of life, the hemoglobin
concentration was 21.4 gm/100 ml, white blood
cells, 20,1 00/mm3 (corrected) with
polymorpilonu-clear leukocytes 52%, band forms 30%,
metamyelo-cytes 1%, lymphocytes 12%, monocvtes 5% and 22
normoblast.s per 100 white blood cells,
reticulo-cytes 8%. The platelet count was 40,000/mm’.
There was mild anisocvtosis aimd poikilocvtosis of
the red blood cells. Occasional spimerocvtes and
)ykIlocyte5 were seen. The coagulation time was
5 minutes, bleeding time 2 minutes. Time capillarv
fragility test was negative. Tibial bone marrow
aspiration resulted in a cellular specimen with
normoblastic hyperplasia (NI :E ratio of 1 : 1
)
aiid amarked decrease in megakaryocytes. There was no
blood group incompatibility. Time direct
antiglob-uhin test was negative. Bacterial cultures of the
blood, urine and cerebrospinal fluid were sterile.
Tissue culture of urine and saliva for
c’tomegalo-virus performed by Dr. 1-Ienrv Shinefield of the
New York Hospital-Cornell Medical Center, was
negative. The serum calcium was 10.6 mg/100 ml,
phosphorus 4.6 mg/100 ml, and alkaline
phos-phatase 3.4 Bodansky units. Three days after birth the mother’s peripheral l)lOOdl smear showed
ade-quate platelets.
