40 OSTEOPOROSIS OF AGEING

SIR,-We found the paper by Dr Lund and others (Dec. 13, 1168) misleading because of their apparently uncritical use of the terms "osteoporosis" and "osteomalacia". It is surely essential in testing any treatment for osteoporosis to be certain p.

that other bone diseases are excluded. Yet the authors say that 4 of their 7 patients had osteomalacia (by which they mean excess osteoid) and then imply that this may be a feature of "osteoporosis of ageing". There is little doubt that osteomalacia and osteoporosis often occur together in the elderly, but to suggest that one is a feature of the other is to add unnecessary confusion. Moreover, it is impossible to be certain that any of their patients had osteoporosis alone. Thus, of the 3 patients for whom biochemical details are given, all had high levels of serum-alkaline-phosphatase, and 1 was hypocatcfemic; the "increased physical fitness" in no less than 6 of the patients after only 4-5 weeks of treatment is exactly the response one might expect in vitamin-D deficiency. The only evidence that these patients did not have simple vitamin-D deficiency is that all but 1 had normal serum-levels of 25-hydroxycholecalciferol. But these estimations were presumably in blood-samples taken when the patients were in hospital and therefore probably receiving adequate amounts of vitamin D. We would suggest that the authors’ conclusion "that patients with osteoporosis of ageing benefit from treatment with 1&agr;-hydroxycholecalciferol" is acceptable, with reservations, only if it is realised that they are in fact referring to patients with osteoporosis and osteomalacia, and that any benefit may derive from treatment of the osteomalacia. For them to extend their conclusions to elderly patients with uncomplicated osteooorosis seems auite uniustified. -

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K. SMITH

R. J. WALTON C. G. WOODS

Nuffield Orthopædic Centre, Oxford OX3 7LD.

with osteogenesis imperfecta differed both quantitatively and qualitatively from the normal pattern. The amounts of the ethylene-diamine-tetra-acetic-acid soluble fraction and of &agr;2- HS glycoprotein were expressed as a percentage of the organic matrix rather than of the calcified tissue, since it is simpler to interpret and more logical to express data as a function of one variable rather than as a complex function of two or more variables. Most scientists would accept that osteogenesis imperfecta is a clinically and genetically heterogenous disorder. There is a need at present to establish the biochemistry of the defects, and promising ways of accomplishing this seem to be through cellculture and tissue-culture studies and by characterisation of collagen and the other proteins associated with it. These studies should eventually provide objective criteria by which the various forms of the disease can be diagnosed, classified, and eventually understood. Strangeways Research Laboratory, Wort’s Causeway, Cambridge, CB1 4RN.

PITTING TEST AND TRANSFUSION

REQUIREMENTS SIR--The capacity of the myocardium

to cope with the intravenous transfusion following may be estimated by measuring the time taken for the rise in central venous pressure (c.v.p.) produced by rapid infusion of 1-200 ml fluid to return to its previous level. If electrolyte solutions are used, hypoproteinaemia (serum-albumin 3-0 g/dl) may interfere with the test by allowing fluid to pass into the interstitial fluid and so lower the c.v.p.’ A simple test to identify patients with such a condition is described. 10 ml physiological saline is injected subcutaneously into the front of the forearm as superficially as possible without being

extra venous return

OSTEOGENESIS IMPERFECTA

HAEMOGLOBIN AND ALBUMIN LEVELS (MEAN AND GROUPS

SIR,-In his observations (Nov. 22, p. 1043) on our preliminary communication (Sept. 27, p. 586), Dr Smith unfortun-

ately fails to appreciate both the purpose of preliminary communications in general and the objectives of ours in particular. The general purpose is to indicate a potentially worthwhile new line of investigation. We intended to convey, as concisely as possible, the view that the non-collagenous proteins of bone matrix play an important part in bone metabolism and in determining the properties of the mineralised tissue. In support of this we provided preliminary evidence that this protein fraction differs from normal in osteogenesis imperfecta. There is an increasing interest in these non-collagenous proteins and their function in mineralised tissues,’ and it is appropriate that such studies, previously confined mainly to tissue from normal animals, should be extended to man. It was necessary to exclude the detailed clinical information about patients in the interests of brevity, and because this could be dealt with more appropriately in a full publication at a later date. For similar reasons, we did not describe at length the details of the gel-electrophoresis method, which is in any case a widely used technique. Dr Smith’s stated incapacity to interpret the electrophoretic pattern is understandable, since we said that these proteins had not yet been fully characterised by ourselves or by any other group; the reader was invited only to compare patterns from normal and abnormal bone. Inevitably, the number of children-particularly controlswho can be studied by biopsy of the diaphysis of long bones is limited; studies of blood and skin-biopsy specimens are obviously more amenable in this respect. However, our studies of matrix proteins from normal subjects ranging in age from newborn to the seventh decade showed similarities of features and consistency of age-dependant changes, and all 4 patients G., Triffitt, J. T., Holbrook,

I. B. Clin.

Orthop. 1975, 110, 269.

S.D.) IN

PITTING-TEST

The differences between the Hb levels in the three groups are significant, (p

Letter: Osteogenesis imperfecta.

40 OSTEOPOROSIS OF AGEING SIR,-We found the paper by Dr Lund and others (Dec. 13, 1168) misleading because of their apparently uncritical use of the...
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