Contents Editorial Understanding of small, minimum and large sample size 1 and its clinical implications S.N. Dwivedi Facing the challenge of tobacco in India - 3 National Tobacco Control Programme R.K. Srivastava, Jagdish Kaur Commentaries Tele-ophthalmology: a new initiative of 8 National Programme for Control of Blindness (NPCB) Sandeep Sachdeva Paradigm shift in pathology education in India 11 Karuna Rameshkumar, Bipin Batra Occupational health and safety 14 R. Rose, Sandeep Sachdeva Review articles Preeclampsia and associated risk factors 21 Betsy Varughese, Manoj Dhingra, Rani Kumar, Renu Dhingra Renal Tubular Acidosis(RTA) in children 27 Sanjiv Nanda, Ashish Marwah, Poonam Marwah Recurrent pain abdomen in children 33 Venkatesh.C, VishnuBhat.B Neonatal Necrotizing Enterocolitis 37 Prabha, Vishnu Bhat Original Article Assessment of bronchial liability on exposure to isometric 46 Exercise during different phases of menstrual cycle Mona Bedi, V P Varshney, Shilpa Khullar Availability and consumption pattern of iodised salt in 50 the villages of ballabgarh, district, Haryana Radhika Sood, Misha Sharma, Chandandeep Gujral Correspondence Quality control program for HIV diagnostic laboratories – an Indian experience 58 Dimple Kasana Intra abdominal desmoid tumor presenting with bleeding 59 Ram Prakash Gupta 49th Annual conference of the college of Surgeons of West Africa 62 J.K. Bnerjee Klippel Trenaunay Weber syndrome : a case report 63 Deepak Badgujar, M K Mittal, Abhay Aryan, Sheetal Kaur N K Bhambri, B B Thukral 1 Understanding of Small, Minimum and Large Sample Size and Its Clinical Implications Editorial S.N. Dwivedi Department of Biostatistics, All India Institute of Medical Sciences Ansari Nagar, New Delhi basic important question account of objective under study, known as a minimum sample size under planning of a case of one-tail (one-sided) or required to answer that specific Aany study including two-tail (two-sided) test is question under used considera- randomized controlled clinical trial considered. These basic issues tions. Most of the time, as (RCT), especially of phase III, is involved in sample size calculation reported earlier, attempt is made the required sample size 1, 2. My will be explained in future to consider a small sample size experience of working in the field communication. that is smaller than the required of epidemiological research for In developing countries like minimum sample size. It is very more than two decades shows India, without knowing clinical rare that a large sample size is that most of the time meaning implications, an investigator may considered, which means of small, minimum and large purposefully try to consider a consideration of sample larger sample size is misunderstood and small sample size taking into than the required minimum quoted in a wrong sense account all or some of the sample size. Hence, on account of knowingly and/or unknowingly. considerations like higher levels of the need of appropriate clinical Hence, clarifying this issue group specific cure rate, broader practice, there is need to through a reputed journal/ differences in cure rates between communicate reminders from Bulletins becomes essential in groups, lower confidence level, time to time to ensure use of at view of the need of better lower power of the study, higher least minimum sample size if one epidemiological understanding. relative precision, and one-sided really wants to conclude the study. To make the communication test. While doing so,(s)he may To support his stand in favor more effective among the clinical think of that small sample size is of a small sample size, an colleagues, who are quite often enough for his study to answer investigator may argue that a little responsible to plan the study (e.g., the question under study. Further, difference between cure rates may as Student/ Principal Investig- to justify his consideration, he be shown as significant under ator), this issue may be explained may quote statistical theory that a large sample size. Accordingly, taking RCT as a case that is familiar large sample size will show a consideration of a large sample topic for them. small difference in cure rates size may be just wastage of time, In general, RCT involves a between the groups as a money etc. without much clinical problem of testing of hypothesis- significant result. Why should he use. However, he forgets the fact comparison of proportions or unnecessarily consider large that : it is very rare that a large means 3 between treatment sample size which is just wastage sample size, more than required groups (including placebo group, of time, money etc.? This type of minimum sample size, is if any). In view of specific practice or thinking itself comes considered. Sometimes, a large objective of the trial, using best mainly because of misconceptions sample size being quoted by him available probable information like misunderstanding of may be even less than required (e.g., group specific cure rate) on meanings of small, minimum minimum sample size to answer the topic under investigation, the and large sample size. a specific question under required sample size is calculated As a matter of fact, in general investigation. He may be doing at considered level of confidence practice, required sample size so only because of a sample size (e.g., 95%), power of the study calculated with all valid scientific which involves much time and (e.g., 90%) and relative precision considerations (inputs) is referred money; consideration of a small (e.g., 10%). Further, again on as a minimum sample size. It is sample size, less than required Journal of Postgraduate Medical Education, Training & Research 1 Vol. IV, No. 1-5, January-October 2009 minimum sample size, may result try to conclude the study that may soon became a widespread in lower power of the study which result into wrong clinical practice. indication for therapeutic may give the message that new References endoscopy. The placement of a drug is as good as old drug. As a 1. Pocock Stuart J. Clinical Trials: PEG tube involves but a few result of this, use of new drug A Practical Approach. John ingenious steps. First, a cannula will come into clinical practice that Wiley & Sons, New York, containing a suture is inserted may not be appropriate in real 1983. through the skin into the sense. Further, as an availability of abdomen of the patient. An new drug, the physicians may get 2. Altman DG. Practical Statistics endoscope is inserted down the tempted to prescribe this more for Medical Research. esophagus to the stomach and the frequently. In reality, new drug Chapman and Hall, India.1991 endoscopist snares the suture may not be appropriate, but : 514-517. from the cannula. The suture is wrong perception/ practice about 3. Fleiss JL.Statistical methods then pulled up through the sample size may result into bad for rates and proportions. esophagus and out of the mouth clinical practice; and consideration John wiley & Sons, New York, where it is tied to the enteral of even large sample size, more 1981. feeding tube. The tube is then than required minimum sample pulled back down through the size, may not have bad clinical Percutaneous hole in the stomach wall and skin implications. If we get significant Endoscopic until it is partly out of the body. result, either old drug may be The mushroom tip on the better than new one or new drug Gastrostomy, 1979 internal end of the tube keeps it may be better than old drug. In in the stomach. After the tube is first case, old drug will continue inserted, nutrients may be fed to be used in clinical practice. In directly into the stomach via second case, use of new drug may syringe after twenty-four hours. not be that much dangerous PEG could be performed either because result being based on a as an inpatient or outpatient large sample size will have more surgery. The procedure eliminated precision (accuracy). In this case, risks associated with laparotomy, we may feel more comfortable including anesthesia complic- using new drug. When patients have difficulty ations, infection, and organ Taking into account above- swallowing, as a result of disease rupture. In their review of 150 mentioned brief facts, it is or injury, a feeding tube can be cases published in the Archives of necessary to consider at least inserted to provide the nutrients Surgery ( August,1983), Gauderer minimum sample size in a RCT/ to sustain life. In 1979, Micheal and Ponsky found no deaths as a other studies making us able to Gauderer, a pediatrician from result of the procedure, and conclude the results without University Hospitals of Cleveland, complications (in only ten percent much distortion in clinical practice. and Jeffrey Ponsky, a University of cases) were minor and easily There is no dispute in a study Hospitals endoscopist, devised treated. The apparatus seen here based on larger sample size in real Percutaneous Endoscopic is the PEG feeding tube and a sense, which will obviously Gastronomy (PEG) to insert syringe that would be used to provide more precise and stable these feeding tubes that was both administer the nutrients. results. Otherwise, if minimum inexpensive and low risk. This sample size is not considered, the procedure comprised an attractive study may be reported as a pilot alternative to laparotomy, a surgical study. In this case, one should not incision of the abdomen, and Journal of Postgraduate Medical Education, Training & Research 2 Vol. IV, No. 1-5, January-October 2009 2 Facing the challenge of tobacco in India - National Tobacco Control Programme Editorial R.K. Srivastava, Jagdish Kaur Directorate General of Health Services, Ministry of Health & Family Welfare, Government of India, Nirman Bhawan, New Delhi obacco is the foremost And during this period, ever The tobacco epidemic has four cause of preventable death smoking of cigarettes had stages, based on the percentage of T and disease in the world significantly increased in the adult male/female smokers and today.