77 ŒSTROGEN THERAPY AND " ETERNAL YOUTH "
Sm,-I read your editorial of June 7 (p. 1282) with interest, particularly the call for a long-term controlled survey of the use of oestrogen replacement therapy after the menopause. Such a project is in fact under way at the Groote Schuur Hospital, Cape Town, based on previous data reported from the menopause clinic. Preliminary results, however, will not be available for at least 2 years. 924 Medipark, Hertzog Boulevard, Cape Town 8001.
WULF H. UTIAN.
POTASSIUM SUPPLEMENTATION OF THIAZIDE THERAPY
SIR,-We wish to comment on the study reported by Dr Wilkinson and his colleagues (April 5, p. 759) as to whether potassium supplementation is necessary in patients with uncomplicated mild essential hypertension treated with prolonged low-dose thiazide diuretic therapy. of the study.-Although the studies were extended longer period than previous investigations of the above specific question, the follow-up period was still only 12 months. Extrapolations from such results to patients treated for up to 10 or more years might therefore not be valid. Thus the authors’ conclusion, as stated in the summary, " that routine potassium supplements are not essential in the treatment of uncomplicated essential hypertension with thiazide diuretics" may not be 1. Duration
for
a
warranted from their own short-term data. 2. Data presented.-In the methods section it is stated that " The standard error on a measurement of T.B.K. (total body potassium) was approximately 3-5%." This is presumably derived from previous data not quoted, since it is obviously not the standard error of the measurement in the patients under study, who did not appear to havehadmorethan one measurement at any one time. No comment is made as to weight change in the subjects studied. This aspect is important, since a change in weight is accompanied by a corresponding change in T.B.K.l Neither was any comment made on the long-term quality control of the measurements of serum potassium, sodium, bicarbonate, or urea. This aspect is particularly important and was presumably checked. 3. Deductions made.- The authors state in their summary, " There was no significant decrease in T.B.K. in the same period " (12 months) and in their text " The average decreases in serumpotassium and T.B.K. in our patients at 12 months (0-40 mmol per litre and 3-4%, respectively) were so small as to be of doubtful clinical significance."
However, there are several points concerning the significance of the results to which we should like to draw attention. While a decrease of 3-4% in T.B.K. after one year seems small as a percentage, it represents a clinically significant loss of 120 mmol of potassium from a total body pool of 3500 mmol in a 70 kg. man.2A decrease in serumpotassium by 0-40 mmol per litre is likewise far from clinically insignificant whether expressed as a percentage (a 9-4% decrease) or in absolute terms. The authors obtained P values 0-10 >p> 0-05 and 0-02 for changes in T.B.K. and serum-potassium, respectively, at 12 months. These values are not statistically significant. However, it is not clear from their article which statistical technique they have used or on what raw data they have obtained their P value for T.B.K. It would appear that the authors have used percentage values for T.B.K. to obtain their P value. When we analysed the data presented in the paper we obtained rather different P values of
Sm,-I read your editorial of June 7 (p. 1282) with interest, particularly the call for a long-term controlled survey of the use of oestrogen replacement therapy after the menopause. Such a project is in fact under way at the Groote Schuur Hospital, Cape Town, based on previous data reported from the menopause clinic. Preliminary results, however, will not be available for at least 2 years. 924 Medipark, Hertzog Boulevard, Cape Town 8001.
WULF H. UTIAN.
POTASSIUM SUPPLEMENTATION OF THIAZIDE THERAPY
SIR,-We wish to comment on the study reported by Dr Wilkinson and his colleagues (April 5, p. 759) as to whether potassium supplementation is necessary in patients with uncomplicated mild essential hypertension treated with prolonged low-dose thiazide diuretic therapy. of the study.-Although the studies were extended longer period than previous investigations of the above specific question, the follow-up period was still only 12 months. Extrapolations from such results to patients treated for up to 10 or more years might therefore not be valid. Thus the authors’ conclusion, as stated in the summary, " that routine potassium supplements are not essential in the treatment of uncomplicated essential hypertension with thiazide diuretics" may not be 1. Duration
for
a
warranted from their own short-term data. 2. Data presented.-In the methods section it is stated that " The standard error on a measurement of T.B.K. (total body potassium) was approximately 3-5%." This is presumably derived from previous data not quoted, since it is obviously not the standard error of the measurement in the patients under study, who did not appear to havehadmorethan one measurement at any one time. No comment is made as to weight change in the subjects studied. This aspect is important, since a change in weight is accompanied by a corresponding change in T.B.K.l Neither was any comment made on the long-term quality control of the measurements of serum potassium, sodium, bicarbonate, or urea. This aspect is particularly important and was presumably checked. 3. Deductions made.- The authors state in their summary, " There was no significant decrease in T.B.K. in the same period " (12 months) and in their text " The average decreases in serumpotassium and T.B.K. in our patients at 12 months (0-40 mmol per litre and 3-4%, respectively) were so small as to be of doubtful clinical significance."
However, there are several points concerning the significance of the results to which we should like to draw attention. While a decrease of 3-4% in T.B.K. after one year seems small as a percentage, it represents a clinically significant loss of 120 mmol of potassium from a total body pool of 3500 mmol in a 70 kg. man.2A decrease in serumpotassium by 0-40 mmol per litre is likewise far from clinically insignificant whether expressed as a percentage (a 9-4% decrease) or in absolute terms. The authors obtained P values 0-10 >p> 0-05 and 0-02 for changes in T.B.K. and serum-potassium, respectively, at 12 months. These values are not statistically significant. However, it is not clear from their article which statistical technique they have used or on what raw data they have obtained their P value for T.B.K. It would appear that the authors have used percentage values for T.B.K. to obtain their P value. When we analysed the data presented in the paper we obtained rather different P values of
