Monday, November 22, 2010

Medecins Sans Frontieres (MSF) - Doctors Without Borders! Vacancy notice for MD-Obs n Gynae

Medecins Sans Frontieres  (MSF) - Doctors Without Borders!

MSF is constantly looking out for medical professionals for their projects
in India as well as for emergency interventions. 

At present there is a vacancy notice for MD-OBG (MD Obs and Gynae) at our project in Bijapur, Chhattisgarh

If you wish to join, please submit your letter of interest and CV to <>

Monday, September 6, 2010

What is Lyophilization ?

We read of lyophilize vaccines and it is but natural that this question comes to our mind. Lyophilization or freeze drying is a process in which water is removed from a product after it is frozen and placed under a vacuum, allowing the ice to change directly from solid to vapor without passing through a liquid phase. e.g. Measles, BCG vaccine, antibiotics etc.

What is meant by waste disposal ?

During the course of teaching I found that students considered the collection of wastes in dustbins as disposal of waste. This is actually waste collection and not disposal. The steps involved in waste management is waste generation, collection, transportation and disposal. Waste disposal is the final treatment and disposal in waste management process. For more details click on the following link which tells how the waste disposal is defined by Basel Convention, European Union and OECD/Eurostat Joint questionnaire

Sunday, August 29, 2010

If I started Hepatitis B immunization and did not complete the course, what should I do ?

According to guidelines created by the Centers for Disease Control and Prevention (CDC) you do not have to restart the vaccine series if you received only one or two doses - even if it has been a few years since your last dose of the vaccine. You only need to complete the series by getting the remaining shot(s).

Saturday, August 14, 2010

Recrudescence and relapse in Malaria

Recrudescence is a re-attack of malaria because of the surviving malaria parasites in red blood cells. Characteristic of P.malariae infections. This may be short term or delayed.
Relapse is a re-attack of malaria because of infection by the malarial parasites which were surviving in the liver (i.e. hypnozoites). This is usually a delayed feature.

Vector competence and vectorial capacity

Vector competence refers to the ability of mosquitoes to receive a disease agent microorganism (arbovirus etc.) from the reservoir host and then later transmit the infectious agent to another susceptible host.
Vectorial capacity includes a number of factors like vector competence, mosquito population density, host preferences, biting rate, immunity of the mosquitoes etc.
To be an effective vector, mosquitoes must have a high vector competence and vectorial capacity.

Wednesday, August 4, 2010

In infectious disease epidemiology; what is the difference b/w vehicle and fomite ?

A vehicle is a substance which can carry a microorganism into your body. e.g. air, water or food. A fomite is an object which is capable of retaining a microorganism, and may be a source of infection.

Tuesday, August 3, 2010

What are 'standards', e.g. as in Indian Public Health Standards (IPHS) ?

Standards are a means of describing the level of quality that health care organizations are expected to meet or aspire to.
In contrast to standards, 'norms' are the typical expected patterns of a particular group.

Friday, July 23, 2010

Kangra valley pilot project - the pioneer of National Iodine Deficiency Disorder Control Programme in India

In order to find out whether iodine deficiency is a causative factor of endemic goiter in the Himalayan belt and to find out the effectiveness of iodine prophylaxis, a prospective study was organized in 1956 in Kangra valley of Himachal Pradesh in India. (Sooch and Ramalingaswami, 1965). The study region was divided into A,B and C zones. After a baseline survey in 1956, the salt distributed to zones A and C was fortified with potassium iodide and potassium iodate, respectively, while zone B was supplied with unfortified salt. The salt fortification was at a level that supplied approximately 200 microgram of iodine per person per day. After six years of iodization, in 1962, a marked decrease in the prevalence of goiter was observed in zone A (from 38% to 19%) and zone C (38% to 15%) without any significant change in zone B. Six years later, in 1968, a systematic survey of goiter prevalence showed a further reduction in zones A and C (8.5% and 9.1% respectively). This project laid the foundation of National Goiter control project which later on was changed to National Iodine deficiency disorder control programme in India.

Tuesday, July 20, 2010

Secondary attack rate and Basic reproductive rate; what is the difference?

Secondary attack rate (SAR) is the proportion of susceptibles infected by getting exposed by one diseased individual in one incubation period. 

Basic reproductive rate; whereas is the potential for a contagious disease to spread from person to person in a population (in which all are susceptible). The basic reproduction rate (BRR) takes into account the population dynamics as we can know by this formula:
BRR= a x b x d
where; a is the risk of transmission per contact; b is the number of such contacts that an average person in the population would normally have per time unit and d is the duration of infectivity of an infected person, measured in the same time unit as b was. 

We find that the formula is very trivial (which i hv tried to keep for explaining the basic concept) and tells us that if the risk of transmission per contact is high, the number of contacts is also high among the people
in a population and the duration of infectivity of the diseased person is high then the BRR or the potential for a contagious disease to spread in a population will by high.
These all things are not taken into account by the Secondary attack rate which is very much representative of a fixed (static) model estimate whereas BRR is representative of a dynamic model estimate. 

Tuesday, June 1, 2010

Define 'source' of infection

The source of infection is defined as "the person, animal, object or substance from which an infectious agent passes or is disseminated to the host"

Define Reservoir for a disease

A reservoir is defined as "any person, animal, arthropod, plant, soil or substance (or combination of these) in which an infectious agent lives and multiplies, on which it depends primarily for survival, and where it reproduces itself in such manner that it can be transmitted to a susceptible host" 

Sunday, May 16, 2010

Funding pattern in ICDS

  1. ICDS is a Centrally-sponsored Scheme implemented through the State Governments/UT Administrations. Prior to 2005-06, 100% financial assistance for inputs other than supplementary nutrition, which the States were to provided out of their own resources, was being provided by the Government of India. Since many States were not providing adequately for supplementary nutrition in view of resource constraints, it was decided in 2005-06 to support to States up to 50% of the financial norms or to support 50% of expenditure incurred by them on supplementary nutrition, whichever is less.
  2. From the financial year 2009-10, Government of India has modified the funding pattern of ICDS between Centre and States. The sharing pattern of supplementary nutrition in respect of North-eastern States between Centre and States has been changed from 50:50 to 90:10 ratio. So far as other States and UTs, the existing sharing pattern of 50:50 continues. However, for all other components of ICDS, the ratio has been modified to 90:10(100% Central Assistance earlier).

Why P=0.05?

Why P=0.05?
A very good article on p value.

Sunday, May 2, 2010

Error bars and statistical significance

If two SE error bars overlap you can conclude that the difference is not statistically significant, but when the two SE error bars do not overlap, you cannot draw any conclusion regarding statistical significance.

Wednesday, April 28, 2010

What is there in a name ? Changing the nomenclature of Comm Medicine.

Well, selecting a particular name for a specialty is a very serious issue. Its like we are on the verge of making history. 
Therefore it has to undergo a well structured and organised debate and a highly focussed discussion which involves all the stakeholders (Community Medicine professionals working in all the sectors and past and present students of Community Medicine). This is because we should know that by the nomenclature of Community Medicine, what opportunities and challenges one has faced or is expecting to face in future.
The advantages and disadvantages of a particular nomenclature have to be discussed in depth. For example a MD (Community Medicine) student may face a problem while going abroad where Public Health is only recognized and not Comm Med. This takes away from the student the opportunity just because of the difference in nomenclature. 
The other issue, which I think should be highlighted is; not just the nomenclature; but we should also strive for a standardized curriculum for MD (Comm Med). 
We have a responsibility; that the future generation of Community Medicine professionals should stand up with pride and have a clear sense of direction and understanding and not getting confused as to what and where they belong because of a nomenclature based on no debate.
When the future generation thinks about the name of their specialty they should have clear, logical and evidence based answers (the time to find this is now) rather than coming to know that the nomenclature was decided just by an opinion poll and the name which got the maximum votes got selected. 

We should be driven by evidences and information and not by popular votes.

Suggestions/comments are welcome.

Sunday, April 25, 2010

Signal to Noise Ratio Concept in biostats...

I would like to share this wonderful concept that forms the basis of many theories in biostats.

This originates from the signals received by radio transmitters.If the sound is not clear, we say it is noise. The sound has to cross a certain threshold level to be labelled as a 'signal'. This is analogous to the 'within group variances' (compared to 'noise') and 'between group variances' (compared to 'signal').

Ratio of variances between the groups to variance within the groups is known as F-ratio that we use in comparing more than two groups by ANOVA method.

Now, there emerges four possibilities from this analogy. These are:
1. Signal present and detected
2. Signal present but not detected
3. Signal absent and no signal detected
4. Signal absent but signal detected
The first and third points are detecting the facts. In the second and fourth point, we find that these are errors. Not detecting a signal when it is present is what we call as a type II error (the opposite of which, i.e. detecting a signal when present is power). Similarly, detecting a signal when there is none is the type I error.

I have found my life easier (not in every way but w.r.t. type I and type II errors) after this concept and hope the same for the reader of this post.
Bye for now.....

Sunday, April 11, 2010

Homoscedasticity. Oops !! What's that ?

Homo = same; Scedastic = scatter (which we know by the name of 'variance' in statistics).
Before applying t-test, don't we find a term known as 'equality of variances' between the groups, which is done by the Levene's test. This is for testing homoscedasticity only. This is actually done by dividing variance of one group by variance of another group.
i.e.  .
If this ratio is much different from 1 (for which we always have table already generated by gr8 grandfathers of statistics), we say that the groups are not homoscedasctic.
One more application of this, we commonly find is that in calculating correlations in General Linear Model.
This is homoscedastic, as the scatter is uniform
This is non-homoscedastic (a.k.a. heteroscedastic), as the scatter is non-uniform.
In General Linear Models, to know the correlations, this is one of the assumptions to be met; the other assumptions being that the data should be normally distributed and there should be linearity present in the scatter. bye for now, folks...

Thursday, April 8, 2010

Difference between 'Accuracy' and 'Precision' in statistics

Accuracy is nearing the actual value, where as precision is the degree of reproducibility around the same result.

 High accuracy, but poor precision
 High precision, but poor accuracy

In Epi cluster sampling how does the sample size come to be 210 ?

The formula for sample size calculation for prevalence in community based studies is:
n = (z x z x p x q)/(dxd)
= (1.96)2(0.5)(0.5)/0. 12
= (3.84)(0.25)/0.01 = 96
Taking design effect =2, the total sample size becomes 96 x2 i.e. 192
For a 30 cluster technique, number of subjects to be selected per cluster = 192/30 = 6.4 (rounded up to 7)

That means we have to select 30 clusters, each with 7 units making a total sample size of 30 x 7 = 210 !!!
Interesting, isn't it ??

Wednesday, April 7, 2010

Laverack's domains of Community empowerment

These are the nine organizational areas of influence on community empowerment in a programme context:
(i) participation; (ii) leadership; (iii) problem assessment; (iv) organizational structures; (v) resource mobilization; (vi) links to others; (vii) ‘asking why’; (viii) programme management; and (ix) the role of the outside agents
For more details follow the link:

Indian Diabetes Risk Score developed by Madras Diabetes Research Foundation

CURES also looked at the development of a risk score for diabetes prediction and prevention. One simple way of screening a large population for type 2 diabetes is by development of a simple risk score based on data that can be routinely used at the primary care level. Indian Diabetes Risk Score [IDRS] was developed based on the phase 3 data from CURES. Using statistical analysis, we determined the risk factors, which best predicted diabetes. The IDRS is based on the answers to four simple questions and a simple measurement.
Age [years]< 35 [reference]
35 - 49
> 50
Abdominal obesity Waist <80 cm [female] , <90 [male] [reference]
Waist 80 – 89 cm [female], 90 – 99 cm [male]
Waist > 90 cm [female], > 100 cm [male]
Physical activityVigorous exercise or Strenuous work
Moderate exercise work / home
Mild exercise work / home
No exercise & Sedentary work / home
Family historyNo family history
Either parent
Both parents
Maximum score100
Source : Dr. V. Mohan, et al, J Assoc Physicians India, 2003
An IDRS value > 60 had the optimum sensitivity (72.5%) and specificity (60.1%) and accuracy of 61.3%, for prediction of diabetes in an individual. This simplified Indian Diabetes Risk Score is useful for identifying undiagnosed diabetic subjects in India and could make screening programmes more cost effective as it can reduce the cost by 50% if replaced for screening programmes with blood sugar estimations.

Difference between 'pilot study' and 'pretesting' in research methodology

Most of the times these terms are used interchangeably. The International Development Research Centre Canada site mentions this difference between them:

A PRE-TEST usually refers to a small-scale trial of particular research components.
A PILOT STUDY is the process of carrying out a preliminary study, going through the entire research procedure with a small sample.

Friday, March 19, 2010

Revised recommendations for Rabies postexposure prophylaxis

Previously, Advisory Committee Immunization Practices recommended a 5-dose rabies vaccination regimen with human diploid cell vaccine (HDCV) or purified chick embryo cell vaccine (PCECV). These new recommendations reduce the number of vaccine doses to four. The reduction in doses recommended for PEP was based in part on evidence from rabies virus pathogenesis data, experimental animal work, clinical studies, and epidemiologic surveillance. These studies indicated that 4 vaccine doses in combination with rabies immune globulin (RIG) elicited adequate immune responses and that a fifth dose of vaccine did not contribute to more favorable outcomes. For persons previously unvaccinated with rabies vaccine, the reduced regimen of 4 1-mL doses of HDCV or PCECV should be administered intramuscularly. The first dose of the 4-dose course should be administered as soon as possible after exposure (day 0). Additional doses then should be administered on days 3, 7, and 14 after the first vaccination. ACIP recommendations for the use of RIG remain unchanged. For persons who previously received a complete vaccination series (pre- or postexposure prophylaxis) with a cell-culture vaccine or who previously had a documented adequate rabies virus-neutralizing antibody titer following vaccination with noncell-culture vaccine, the recommendation for a 2-dose PEP vaccination series has not changed. Similarly, the number of doses recommended for persons with altered immunocompetence has not changed; for such persons, PEP should continue to comprise a 5-dose vaccination regimen with 1 dose of RIG. Recommendations for pre-exposure prophylaxis also remain unchanged, with 3 doses of vaccine administered on days 0, 7, and 21 or 28. Prompt rabies PEP combining wound care, infiltration of RIG into and around the wound, and multiple doses of rabies cell-culture vaccine continue to be highly effective in preventing human rabies. 
Source: accessed on March 19, 2010

'Source-sink' dynamics in polio transmission

  • Sources are areas or location where local reproductive success is greater than local mortality (>0)
  • Sinks are areas where individuals are reproducing, but the net reproductive rate is <0 (not replacement)
  • Sinks will eventually become extinct if they do not receive immigrants from other areas.
In polio virus transmission it is found that if from one place the virus is eradicated but it may come from other place where polio virus is still circulating, thus maintaining the transmission. For example, Uttar Pradesh and Bihar are acting as 'sources' and the other places in India from where the polio virus transmission has been reduced act as 'sinks'.

Thursday, March 18, 2010

Food enrichment vs. fortification

Many a times we come across these terms on packets of food items and get confused, as more or less they seem to mean the same. Food enrichment is in fact the addition of nutrients so as to restore the amount lost by processing, storage etc. For example, addition of vitamin C to orange juice in order to compensate for the loss due to processing etc. is enrichment. On the other hand, fortification is the addition of those nutrients to food items that was not naturally present in them. Addition of Iodine to common salt is therefore an example of food fortification.