780

Regarding the statement that children with P.C.M. maybe endangered by smallpox vaccination, we should like toshare their concern. In 1964 Viteri 9 informed us ofseveral children with kwashiorkor in Guatemala who werevaccinated against smallpox in the early recovery phaseand developed generalised vaccinia. On the other hand,in a group of children who were in a chronic state of P.C.M.,as defined by a number of biochemical parameters, weobserved no ill effects attributable to smallpox vaccination. 10All the vaccinated children developed normal self-limitedprimary reactions.

College of Physicians and Surgeons,Columbia University,

New York, N.Y. 10032, U.S.A. MICHAEL KATZ.

Mount Sinai School of Medicine,New York, N.Y. 10029. ROY E. BROWN.

HEATING ACTION GROUP

SiR,—The Heating Action Group has been set up to

help those who cannot afford to keep warm. Many oldpeople and poor families are still unable to afford adequateheating, or pay for heating at the cost of adequate diet orother necessities. We hope and believe that the medical ornursing professions can help in our campaign. A recentnational survey 11 showed that 74% of elderly people wereunaware they might be eligible for an extra heating al-lowance from the Supplementary Benefits Commission.Where doctors, health visitors, and others know of casesof " heating hardship ", may we ask them to provide us withdetails and give this address to those who may be needinghelp ? We are very pleased to supply on request copies ofour guide on heating allowances or notices (for waiting-rooms ?) about the Heating Action Group.

1 Macklin Street,Drury Lane,

London WC2B 5NH. MARIGOLD JOHNSON.

ARGININE-GLYCINE AMIDINOTRANSFERASEACTIVITY IN MYOTONIC DYSTROPHY

SIR,-In 1969 Harvey reported that the activity of theenzyme arginine-glycine amidinotransferase (A.G.A.; E.C.2.1.4.1.) was reduced in the renal cortical tissue from 2patients with myotonic dystrophy. 12 This enzyme is respon-

A.G.A. ACTIVITY IN MYOTONIC DYSTROPHY

sible for the formation of guanidoacetic acid, an inter-mediate in the synthesis of creatine. Harvey also reportedthat urinary excretion of guanidoacetic acid is significantlyreduced in patients with myotonic dystrophy.l3 We havepublished the results of a study in which we found urinaryexcretion of guanidoacetic acid to be normal in myotonicdystrophy,14 but, since kidney tissue from a patient wasnot available, we were unable to establish directly whether

9. Viteri, F. Personal communication, 1964.10. Brown, R. E., Katz, M. Trop. geog. Med. 1966, 18, 125.11. Fox, R. H., Woodward, P. M., Exton-Smith, A. M., Green, M. F.,

Donnison, D. V., Wicks, M. H. Br. med. J. Jan. 27, 1973, p. 200.12. Harvey, J. C. Johns Hopkins med. J. 1969, 125, 270.13. Harvey, J. C. Trans. Am. clin. clim. Ass. 1963, 74, 176.14. Bolton, C. E., Emery, A. E. H. J. Neurol. Neurosurg. Psychiat.

1972, 35, 801.

A.G.A. activity was reduced. However, we have since hadthe opportunity to measure A.G.A. in the kidney cortexfrom a patient with myotonic dystrophy, and we found it tobe normal (see accompanying table). We think it unlikelythat A.G.A. is of importance in the pathogenesis of myotonicdystrophy.

University Department ofHuman Genetics,

Western General Hospital,Edinburgh EH4 2HU.

C. E. BOLTONA. E. H. EMERY.

FALSE-NEGATIVE TESTS FOR URINE

GLUCOSE

SIR,-False-negative tests for glycosuria by the glucose-oxidase dipstick method can be caused by a variety ofagents, including ascorbic acid, in the urine. 1 False-negative tests can be recognised by adding one drop of0-5% glucose to all negative dipstick test areas, and seeingwhether the area then reacts or remains negative.We were interested in several additional questions:(1) How frequently do false-negative tests occur ?(2) Can one identify the interfering agent as ascorbic acid by

using ’ Clinitest ’ tablets ?(3) How strong are these interfering agents ?(4) Are some commercial dipstick preparations more liable

to false-negative reactions than others ?

We tested 47,750 consecutive negative routine urinalysesin a busy general county hospital. Our routine screeningtest for glycosuria was the ’ Bililabstix ’. 170 (0-35%) gavefalse-negative tests for glucose. We then tested 119 ofthese 170 false-negative urines with clinitest tablets.Of these, 49 (41%) were positive, indicating a reducingsubstance, such as ascorbic acid, as the interfering agent.

Next, an effort was made to gauge the strength of theinterfering agent. 47 of the false-negative urines wereadjusted to a glucose concentration of 100 mg. per 100 ml.,and retested with bililabstix. 40 of them (850/) remainednegative. This indicates the inhibition to be strong.These urines were then retested with clinitest tablets andwere all positive, which is not surprising since glucose andascorbic acid are additive for clinitest tablets.The tests were duplicated using ’ Ketodiastix’ and

Testape ’ (Lilly) on 75 urines that were falsely negativewith bililabstix. The ketodiastix is presumably designedby the manufacturer so that low levels of ascorbic acid do notinterfere with the glucose-oxidase test. The testape hasbeen stated to have an advantage in that the paper stripmay be used for the chromatographic separation of glucosefrom the various inhibitors. The testape may give a posi-tive reaction at the upper end of the strip, if glucose is

separated from the inhibitor. Our results showed that theketodiastix was positive in 3 of 75 (4%), while all the

testape tests were negative. This indicates no significantproduct superiority among the various commercial test

preparations.In summary, 0-35% of routine urines tested in a general

hospital gave false-negative reactions with bililabstix, keto-diastix, and testape. Clinitest tablet testing suggested thata reducing substance such as ascorbic acid was responsiblein 41% of the cases. To detect false-negative reactions,one can place one drop of 0-5% glucose on all negativedipstick tests. If the area remains negative, the urinespecimen may be examined with the clinitest tablet. Theresults should be interpreted with caution since ascorbicacid will inhibit the glucose-oxidase test but will act as areducing agent in the clinitest test.1 In cases of a false-

1. Mayson, J. S., Schumaker, O., Nakamura, R. M. Am. J. clin. Path.1972, 58, 297.

2. Feldman, J. M., Kelly, W. N., Lebovitz, H. E. Diabetes, 1970, 19,337.

781

negative glucose-oxidase test, the laboratory should reportthe presence of an interfering inhibitor with the urinaryglucose test and recommend serum-glucose determinationsif necessary.

Department of Pathology,Orange County Medical Center,

101 City Drive South,Orange, California 92668, U.S.A.

JAMES S. MAYSONOMA SCHUMAKERROBERT M. NAKAMURA.

SUSTAINED-RELEASE LEVODOPA IN

PARKINSONISM

SIR,-A sustained-release preparation of levodopa(’Brocadopa Temtabs ’) was found to be clinically slightlyless effective than standard levodopa by Eckstein and hercolleagues. This is in keeping with the finding that plasma-dopa levels at 4-8 hours after a single oral dose of thesustained-release preparation are lower and not higherthan those produced by standard levodopa.The plasma-dopa levels and clinical response to the same

dosage of levodopa or sustained-release levodopa werestudied in 10 patients with paralysis agitans who hadpreviously been on a stable levodopa dosage. The patients(4 male and 6 female, aged from 55-65) all showed somevariation in clinical response during the day, but in nonedid this amount to an " on-off " response. Disability scores(a high score indicating considerable disability) beforetreatment were from 25-80, and on levodopa from 18-45.2These patients were given levodopa for one week and thesame dose of the sustained-release preparation for anotherwith random allocation of treatment period. The dosageof levodopa (0-5-4-0 g. per day) and the time of adminis-tration were kept constant in each patient. The clinical

disability was scored on two weekdays on each preparationat 10.00 and 14.00 hours. On a different day the plasma-dopa levels resulting from a single dose of each preparationwere determined, samples of blood being taken before andat 1, 2, 4, 6, and 8 hours after dosage. The levodopadosage used in this dopa-load test was determined by thepatient’s previous response and was lower than that causingnausea. It varied from 250 mg. to 1-5 g. and the same dosageof the standard and the sustained-release preparation wasused in the two dopa-load tests each patient had. All

patients were given metoclopramide 10 mg. 30 minutesbefore the dopa-load test. Plasma-dopa levels (meani:: 1S.E.M.) (method of Curzon et al.3) were:

Patients were asked to give a preference for the treatmentperiod. Only 2 could express a clear preference, 1 for thesustained-release form and the other for standard-releaselevodopa. The first patient described a more constantresponse throughout the day. 3 patients who had nauseaand vomiting on standard levodopa had similar symptomson the other preparation. Involuntary movements occurredin 5 patients on both forms with apparent equal severityand no clear difference in timing.The difference in the mean total disability scores between

the two preparations was not statistically significant, eitheras assessed in the morning or in the afternoon (p > 01). Themean scores for tremor in the morning and rigidity in the

1. Eckstein, B., Shaw, K., Stern, G. Lancet, Feb. 24, 1973, p. 431.2. Marsden, C. D., Barry, P., Parkes, J. D., Zilkha, K. J. J. Neurol.

Neurosurg. Psychiat. 1973, 36, 10.3. Curzon, G., Kantamaneni, B. D., Trigwell, J. Clinica chim. Acta,

1972, 37, 335.

afternoon were both a little lower whilst on the sustained-release preparation (P in both cases > 0-05). There was no

statistically significant difference in the mean plasma-dopalevels at each measurement time with the two preparations;the mean plasma-dopa concentration after sustained-releaselevodopa was slightly, but not significantly, higher at 1 hour,equal at 2 hours, and lower at subsequent times.These results suggest there is no practical advantage to

be gained by the use of an oral sustained-release preparationof levodopa which in this study resulted in a slightly lowerconcentration of dopa in the plasma 4-8 hours after ingestionthan was given by standard levodopa. In view of the highconcentration of dopa decarboxylase in the gut wall, thisresult might be expected; the longer levodopa remains incontact with gut epithelium the greater may be the break-down to dopamine therein and the smaller the amount ofdopa available for absorption.

Institute of Neurology,Queen Square, London.

G. CURZONJUNE FRIEDEL.

King’s College Hospital,London SE5 9RS.

LINDA GRIERC. D. MARSDENJ. D. PARKESM. SHIPLEYK. J. ZILKHA.

IMMUNOCOMPETENCE OF LYMPHOCYTESFROM OSTEOSARCOMA PATIENTS

SIR,-Determination of the proliferative response ofhuman peripheral-blood lymphocytes to phytohaemag-glutinin (P.H.A.) stimulation has been used by many in-vestigators to test the immunocompetence of the thymus-dependent (T) lymphocytes which appear to be the majoreffector cells involved in cell-mediated immune functions

(graft rejection, delayed skin hypersensitivity, and cyto-toxic effect upon neoplastic cells).1-5 Studies of the

integrity of the thymus-dependent immune system in

patients with malignant tumours, as measured by the

response of their lymphocytes to P.H.A. stimulation, havegiven variable and often contradictory results. 6-10 These

investigations, however, generally describe the response in" cancer patients " or

" sarcoma patients " as compared to

controls, rather than specifying the exact types of tumoursstudied. Because of the huge gaps in our present knowledgeof the fundamental basis of malignancy and the body’sresponse to it, we see no reason why all types of cancer, oreven all sarcomas or carcinomas, should have similareffects on cellular immunity.As part of our investigation on the status of the immune

system in patients with osteosarcoma we tested the re-sponse of peripheral lymphocytes in nine patients invarious clinical stages (newly diagnosed with local tumour,local tumour and multiple metastases, long-term survivorswithout apparent residual tumour) to P.H.A. stimulation.Lymphocytes were separated from peripheral blood bycentrifugation on a ’Hypaque-Ficoll’ density gradient."Lymphocyte cultures containing 1 - 106 cells per tube in3 ml. of EBME medium were incubated for three days at

1. Fudenberg, H. H., Good, R. A., et al. Pediatrics, 1971, 47, 927.2. Daguillard, F. Med. Clins N. Am. 1972, 56, 293.3. Sinkovics, J. G., Dreyer, D. A., et al. Texas Rep. Biol. Med. 1971,

29, 227.4. Cheema, A. R. Proc. Am. Ass. Cancer Res. 1971, 184.5. Hellstrom, I., Hellstrom, K. E., Sjogren, H. O., Warner, G. A.

Int. J. Cancer, 1971, 7, 1.6. Garrioch, D. B., Good, R. A., Gatti, R. A. Lancet, 1970, i, 618.7. Nelson, H. S. J. natn. Cancer Inst. 1969, 42, 765.8. Sutherland, R. M., Inch, W. R., McCredie, J. A. Cancer, N.Y.

1971, 27, 514.9. Humphrey, L. S. Proc. 7th natn. Cancer Conf. (in the press).

10. Humphrey, L. S. Ann. Surg. 1968, 168, 374.11. Boyum, A. Scand. J. Lab. clin. Med. 1968, 21, suppl. 97, 77.