Utility of Spot Testing Kit in the Assessment of Iodine Content of Salt- A Multicentric  Study

 

 

Department of Human Nutrition

All India Institute of Medical Sciences

New Delhi-110029

 

1999


Principal Investigators

 

1.    Dr. Subhadra Seshadri,

       Head,

       Department of Foods & Nutrition,

       M S University, Baroda,

       Gujarat.

 

2.    Dr. S. S. Swami,

       Head,

       Department of Prevalence and Social Medicine,

       S. P. Medical College,

       Bikaner, Rajasthan.

 

3.    Ms. Beena,

       Chief Co-ordinator,

       Mamta Samajik Sanstha,

       53-c, Rajpur Road,

       Deharadun.

 

4.    Dr. B.P. Mathur,

       Reader,

       Department of Preventive and Social Medicine,

       Medical College,

       Jhansi (U.P.)

 

5.    Dr. T.D. Sharma,

       Principal,

       Health and Family Welfare and Social Medicine,

       Kangra,

       District Kangra (H.P.)

 

6.    Dr. Kumud Khanna,

       Director,

       Institute of Home Economics,

       New Delhi.

 

7.    Dr. Rita Singh Raghuvanshi,

       Reader & Senior Research Officer,

       Deptt. of Foods & Nutrition,

       GBPUAT, Pantnagar,

       District Udham Singh Nagar (U.P.)

 

8.    Dr. Umesh Kapil,

       Additional Professor,

       Department of Human Nutrition and Gastroenterology,

       All India Institute of Medical Sciences,

       New Delhi-110029.

 

       And

      

       Dr. S.N. Dwivedi,

       Associate Professor and Head,

       Department of Biostatics,

       All India Institute of Medical Sciences,

       New Delhi-10029

       (Central Co-ordinating Unit)


Editors

 

Dr. Umesh Kapil

Additional Professor,

Human Nutrition Unit,

All India Institute of Medical Sciences,

Ansari Nagar, New Delhi-110029.

 

Dr. S.N. Dwivedi

Associate Professor and Head

Department of  Biostatics,

All India Institute of Medical Sciences,

Ansari Nagar, New Delhi – 110029.

 

 

Assistant Editors

 

Monica Tandon*

Priyali Pathak*

Ritu Pradhan*

 

* Research Scientists,

Department of Human Nutrition,

All India Institute of Medical Sciences,

New Delhi-110029


 

List of Contents

 

Contents                                                    

 

1.    Executive Summary                                        

 

2.    Introduction                                                    

 

3.    Objective                                                                  

      

4.    Research Methodology                                             

 

5.    Results                                                           

 

6.    Discussion                                                     

 

7.    References                                                              

 

8.    Appendices                                                    


 

List of Tables

      

 

Tables

 

Table 1         Total Number of Salt Samples Analysed

 

Table 2         Iodine Content of Salt Samples by

                   Iodometric Titration Method

 

Table 3         Iodine Content of Salt Samples at Different centres

                   By Both STK and IT Method

 

Table 4         Analysis of Salt Samples at Different Centres

                   by both STK and IT Method

 

Table 5         Specificity and Sensitivity of STK Against IT Method at Different Centres Studied

 

Table 5.1 Baroda

Table 5.2 Bikaner

Table 5.3 Dehradun

Table 5.4 Jhansi

Table 5.5 Kangra

Table 5.6 New Delhi, IHE

Table 5.7 Udham Singh Nagar

Table 5.8 New Delhi, AIIMS

 

Table 6         Pooled Analysis of Results of Eight Centers

 

Table 7         Sensitivity, Specificity, PPV and NPV of STK

                   against Iodometric Titration Method at

                   different Centres


 

List of Appendices

 

I.     List of Different Centres Participating in the Multicentric

       Study for Assessment of Utility of Spot Testing kit

 

II.    Research Methodology for Collection of Salt Samples

 

III.   Estimation of Iodine Content in salt by Iodometric Titration

 

IV.  Use of Spot Testing Kit

 

V.   Brief Note on Sensitivity and Specificity

 

VI.  Internal Quality Control Procedure Adopted in IT Method

 

VII. Evaluation of Universal Salt Iodisation in India, 1997

       (Excerpts from the detailed report)


 

 

Abbreviations Used

 

AIIMS                    :         All India Institute of Medical Sciences

IDD                       :         Iodine Deficiency Disorders

IHE                       :         Institute of Home Economics

IT                          :         Iodometric Titration

LDPE                    :         Low Density Poly Ethylene

PPM                      :         Parts Per Million

RTM                      :         Research Team Members

STK             :         Spot Testig Kit

UNICEF                 :         United Nations Children’s Fund

WHO                     :         World Health Organization


Acknowledgements

 

       We would like to thank Dr. Sheila Vir, Project Officer, Nutrition, India Country Office, UNICEF for her kind support and guidance during the different stages of the research study. We are grateful to Dr. R Prakash, Salt Commissioner for the help and encouragement extended during the study. We would also like to thank school principal, teachers and students for their kind co-operation in collection of salt samples for the study.


             

1.    Executive Summary   

 

        The use of iodised salt has been evolved as a major strategy to combat Iodine Deficiency Disorders (IDD). IDD are preventable by supplementing the diet regularly with iodine. Iodine concentration to be added in the salt is specified as the number of parts of iodine per million parts of salt, or “ppm”. Salt should contain at least 15 ppm iodine to provide the normal requirements of 150 micrograms per day to the consumer. Careful monitoring and control of iodine levels at the production, storage, sale and consumption stages, and prevention of use of uniodated or substandard iodised salt, are vital components of universal salt iodisation programme. For the successful implementation of this strategy, monitoring the quality of iodised salt is essential. The iodine content of iodised salt is estimated routinely by  the standard “Iodometric Titration” (IT) method in the laboratory. However, a simple Spot Testing Kit (STK) containing starch solution has been advocated as a method for semi-quantitative estimation of iodine content in salt.

 

        The present multicentric study was conducted with the objective to assess the utility of the STK  (against the standard iodometric titration) in the semi-quantitative estimation of iodine in salt.

 

        The study was conducted at eight centres in the country, namely, Baroda, Bikaner, Dehradun, Jhansi, Kangra, New Delhi (IHE), Udham Singh Nagar and New Delhi (AIIMS) co-ordinated by the Department of Human Nutrition, All India Institute of Medical Sciences, New Delhi. Uniform protocol was utilised at all the eight centres to conduct the study.

 

 

 

        The iodine content of more than 700 salt samples at each center (total 6302 salt samples) was estimated by two different methods i.e. IT and STK method and the results were compared.  The results of IT method were used as reference standard for comparison. The Sensitivity, Specificity, Positive Predictive Value (PPV) and Negative Predictive Value (NPV) of the STK method in relation to the IT was calculated, using the standard formulae.

 

        The sensitivity of the STK method reported at different centers ranged from 80.7% to 95.59%,  with an average sensitivity of 89.8% (as calculated after pooling the data of eight centers). The specificity reported from various research centres also ranged from 50.5% to 100.0% with an average specificity of 65.6%.

 

        The present study revealed that for semi quantitative estimation of iodine in salt,  STK method has a high sensitivity but relatively low specificity. These findings suggest that STK method can be used for semi-quantitative estimation of iodine by the government and non-government functionaries for assessment of iodine content of salt for the purpose of monitoring the quality of salt available to the community.

 

        It is further recommended that for monitoring the quality of iodised salt available to the community members, it is necessary to analyze a large number of salt samples to visualize the trend. In this context, the STK can prove a simple and useful tool as compared to IT which requires laboratory facilities.


2.    Introduction

 

        The use of iodised salt has been evolved as a major strategy to combat Iodine Deficiency Disorders (IDD). IDD are preventable by supplementing the diet regularly with iodine. An inexpensive and effective preventive method is to add iodine to salt. Iodine concentration is specified as the number of parts of iodine per million parts of salt, or “ppm”. Salt should contain at least 15 ppm iodine to provide the normal requirements of 150 micrograms per day to the consumer. It is usually necessary to iodate the salt at higher levels (50 ppm or more) to compensate for the loss of iodine in storage and distribution. There are many studies to show that when salt without iodine was provided to population, it has no impact on IDD. On the other hand IDD has been eradicated in many countries by ensuring an effective level of iodine in the salt. Careful monitoring and control of iodine levels at the production, storage, sale and consumption stages, and prevention of use of uniodated or substandard iodised salt, are vital components of universal salt iodisation programme. For the successful implementation of this strategy, monitoring the quality of iodised salt is essential. The iodine content of iodised salt is estimated routinely by  the standard “Iodometric Titration” (IT) method in the laboratory (1). However, recently a simple kit has been developed by MBI chemicals Ltd., Chennai, India for `on the spot’ estimation of iodine content. In the spot testing  method, estimation of iodine content in the salt is done with the help of a standard starch  solution provided in the Spot Testing Kit (STK). The STK has been advocated as a method for semi-quantitative estimation of iodine in salt (2,3).

 

 

3.    Objective

 

        The present study was conducted with the objective to assess the utility of the STK  (against the standard iodometric titration) in the semi-quantitative estimation of iodine in salt.

 

4.    Research Methodology                  

 

        The present multicentric research project was conducted at eight centres in the country, namely, Baroda, Bikaner, Dehradun, Jhansi, Kangra, New Delhi (IHE), Udham Singh Nagar and New Delhi (AIIMS). The research project was co-ordinated by the Department of Human Nutrition, All India Institute of Medical Sciences, New Delhi. Uniform protocol was utilised at all the eight centres  (Appendix I). Research team members (RTM) were provided guidelines for ensuring internal quality control for the IT methods.

 

        The iodine content of each salt sample was estimated by two different methods i.e. IT and STK method and the results were compared.  The results of IT method was used as reference standard for comparison.

 

        More than 700 salt samples were collected at each of the 8 centres selected for the study (Appendix II). Each salt sample was given an identification number and was analysed for its iodine content by IT method (Appendix III) by a research scientist. Subsequently, the salt samples were  recoded and tested again for the iodine content by the STK method (As the scientist was given recoded samples, he was not aware about the results of IT method).

 

        The procedure for use of STK was as follows: The STK consists of a test solution (A), and a  recheck solution (B). One drop of test solution (A) was added to about 5 gm of salt sample. The change in colour of the salt sample ranged from white (no change in colour) to dark violet depending on the iodine content of salt, i.e. Nil, less than 15 ppm, and 15 ppm and above, which was compared with the standard colour chart provided with the STK. If on addition of test solution (A), no change in colour of salt was observed, the recheck solution (B) was added. This was done to make the salt medium acidic, in case the salt had alkaline constituents, subsequently, the test solution (A) was added again. The intensity of the blue colour was directly proportional to the iodine content of  salt (Appendix IV).

 

        For the purpose of present study, the results of iodine content of salt as analysed by STK method was reported under two categories i) salt samples with less than 15 ppm of iodine and ii) salt samples with 15 ppm  and more of iodine.

 

        The Sensitivity, Specificity, Positive Predictive Value (PPV) and Negative Predictive Value (NPV) of the STK method in relation to the IT was calculated, using the standard formulae (Appendix V) (4).

 

        The sensitivity of STK was calculated as the percentage of salt samples truly identified by STK as having 15 ppm and more of iodine content (usually known as positives) of those positives identified by the IT method also. Sensitivity was calculated as the ability of a test (STK) to identify correctly all those salt samples which had more than 15 ppm iodine content; that is, true positive. A 90 per cent sensitivity of STK means that 90 per cent of the salt samples screened by the STK test will give a “true positive” result and the remaining 10 per cent as “false negative” result where negative means samples having less than 15 ppm of iodine content.

 

        Similarly, the specificity was calculated as the percentage of salt samples truly identified by the STK as having less than 15ppm of iodine content (usually known as negatives)  of those negatives identified by IT method. Specificity was calculated as the ability of a test (STK) to identify those salt samples which do not have salt  iodine content  more than 15 ppm, that is, “true negative”. A 90 per cent specificity  of STK means that 90 per cent of the salt samples having iodine content less than 15 ppm will give “true negative” results by the STK test and remaining 10 per cent of the salt samples who have iodine content less than 15 ppm, screened by the STK test will be wrongly classified as having more than 15 ppm iodine content.

 

        The PPV was determined as the percentage of salt samples with iodine content of 15 ppm  or more indicated by IT out of those identified by the STK. On the other hand, the NPV was determined as the percentage of salt samples with less than 15ppm iodine content indicated by the IT method out of those identified by the STK (2).    

 

        Each centre conducted the internal quality control program with each batch of salt samples analysed by them (Appendix VI).

 

        Under National Iodine Deficiency Disorder Control Programme (NIDDCP) it is stipulated that, at the beneficiary level, the salt should contain a minimum of 15 ppm of iodine. In the present study, ability of STK method was compared to correctly identify the salt samples with 15 ppm and more when compared with the standard IT method.

 

4.1   Calculation of Sample Size

 

        With an anticipated agreement between iodometric titration method and spot testing kit as 85% (5)  and assuming ideal agreement as 80%, to have level of confidence of 95% as well as power of the study 95%, the minimum sample size required was calculated to be approximately 660.  To have higher precision, it was decided to undertake study with sample size of 700 at each centre.

 

4.2   Interpretation of sensitivity and specificity

 

        A sensitive test will correctly identify a high proportion of samples of salt that have a stipulated concentration of iodine. A specific test will rarely give a positive result in a sample of salt which actually has less than the specified minimum concentration of iodine. In all spot test, there is a trade off between sensitivity and specificity, the ideal spot test would be one which has both i.e. high sensitivity and high specificity.

       

4.3   Nature of the Spot Testing Kit in Use

 

        All known salt test kits in use are based on the long known ‘iodine/starch’ reaction. The kit which is designed to test for iodate, contains potassium iodide, soluble starch, sulfuric acid and stabilizers. The iodide reacts with iodate, in the presence of acid, to liberate free iodine. The iodine reacts with starch to give a strong blue colour known as the starch-iodine complex.

 

        When the kit reagent is dripped onto dry salt, a blue colour develops, the intensity of which is approximately proportionate to the concentration of iodate in the salt-over a certain range. The intensity of the colour  also depends on other factors which include temperature, colour of the salt, particle size of the salt, moisture content of the salt, and  type of starch used in the preparation of the test kit.

 

5.    Results

 

        A total of 6302 salt samples were collected and analysed at eight different centers in the country out of which 18.8% samples were of crystalline variety (Table 1).  Analysis of salt samples by iodometric titration revealed that 38% samples had less than 15 ppm and 62% had 15 ppm and more of iodine content (Table 2). By STK method 31.3% salt samples had less than 15 ppm of iodine and 68.7% had iodine content of 15 ppm and more (Table 3). Table 4 reveals the results of salt iodine content by STK and IT method.  

 

        The sensitivity of spot testing kit was assessed in terms of the number of salt samples having 15 ppm and more iodine correctly identified by STK method against the total number of salt samples identified as having 15 ppm and more iodine by titration method.

 

        The results of sensitivity and specificity of STK against iodometric titration method assessed at eight different centres in the country has been depicted in tables 5.1 to 5.8. The highest sensitivity of STK was reported by Pant Nagar (Udham Singh Nagar) centre (95.5%). The sensitivity of various research centers ranged from 80.7% to 95.5% (Table 7).

 

        The specificity was determined as the number of salt samples having <15 ppm iodine correctly identified by STK method against the total number of salt samples identified as having <15 ppm iodine by titration method. The specificity of various research centres ranged from 50.4% to 100.0% (Table 7).

 

        The PPV was determined as the percentage of salt samples with iodine content 15 ppm or more as indicated by STK method and titration methods both to the total number of samples with iodine content 15 ppm or more as indicated by the STK method. The positive predictive value of the various research centres ranged from 58.4% to 100.0% (Table 7).

 

        Conversely, the NPV was expressed as the percentage of salt samples with iodine content <15 ppm as indicated by STK method and IT method both to the total number of samples with iodine content <15 ppm as indicated by the STK method. The NPV of the various research centres ranged from 26.8% to 90.4% (Table 7).

 

6.    Discussion

 

        Iodometric titration is the recommended method for assessment of iodine content of salt. However, it requires a laboratory set up and trained manpower. The STK method is simple and can be used by peripheral health functionaries, school teachers, community leaders and traders without any formal training. The STK method is recommended by the Government of India for qualitative assessment of iodine in salt to be used routinely by the government and non-government functionaries. The present study revealed that STK method had an average sensitivity of 89.8% and specificity of 65.6%.

 

        A study conducted by Indian Institute of Health Management Research, Jaipur in 1997 on salt samples collected from seven different states also reported the sensitivity of STK between 77% to 99.2% and specificity from 23.7 to 77.2%  in different states (2) (Appendix VII).

 

        The present study revealed that for semi-quantitative estimation of iodine in salt,  STK method has a high sensitivity but low specificity. These findings suggest that STK method can be used for semi-quantitative estimation of iodine by the government and non-government functionaries. The findings of the present study recommend that STK method can be utilized as a semi-quantitative method for assessment of iodine content of salt only for the purpose of monitoring the quality of salt available to the community.

 

        It is further recommended that for monitoring the quality of iodised salt available to the community members, it is necessary to analyze a large number of salt samples to visualize the trend. In this context, the STK can prove a simple and useful tool as compared to IT which requires laboratory facilities.

 

                        


 

Table 1

Total Number of Salt Samples Analysed at Different Centres

 

Centre

No. of Salt Samples

Type of Salt Sample

Powdered

        n                     (%)

Crystalline

        n                     (%)

Baroda

700

684

(98.0)

16

(2)

Bikaner

700

576

(82.3)

124

(17.2)

Dehradun

797

422

(52.9)

375

(47.1)

Jhansi

855

364

(42.6)

491

(57.4)

Kangra

746

746

(100.0)

0

(0.0)

New Delhi

(IHE)

887

887

(100.0)

0

(0.0)

Udham Singh Nagar

736

676

(91.8)

60

(8.2)

New Delhi

(AIIMS)

881

764

(86.7)

117

(13.3)

Total

6302

5119

(81.2)

1183

(18.8)

 


 

Table 2

Iodine Content of Salt by Iodometric Titration Method at Different  Centres

 

Centre

<15 ppm

15 ppm and More

n

%

n

%

Baroda

208

(29.7)

492

(70.3)

Bikaner

351

(50.1)

349

(49.8)

Dehradun

302

(37.9)

495

(62.1)

Jhansi

461

(53.9)

394

(46.1)

Kangra

49

(6.6)

697

(93.4)

New Delhi (IHE)

455

(51.3)

432

(48.7)

Udham Singh Nagar

168

(22.8)

568

(77.2)

New Delhi (AIIMS)

403

(45.7)

478

(54.3)

Total

2397

(38.0)

3905

(62.0)

 

 

 

Table 3

Iodine Content of Salt by Iodometric STK Method at Different  Centres

 

Centre

<15 ppm

15 ppm and More

n

%

n

%

Baroda

234

(33.4)

466

(66.6)

Bikaner

365

(52.2)

335

(47.8)

Dehradun

240

(30.1)

557

(69.9)

Jhansi

311

(36.4)

544

(63.6)

Kangra

93

(12.5)

653

(87.5)

New Delhi (IHE)

374

(42.2)

513

(57.8)

Udham Singh Nagar

117

(15.9)

619

(84.1)

New Delhi (AIIMS)

239

(27.1)

642

(72.9)

Total

1973

(31.3)

4315

(68.7)

 


 

 

Table 4

 

Iodine Content of Salt Samples by Both IT and STK Methods at different Centres

 

 

Centre

Salt Iodine Content

a*

b*

c*

d*

n

(%)

n

(%)

(n)

(%)

(n)

(%)

Baroda

(n=700)

466

(66.6)

00

(0.0)

26

(3.7)

208

(29.7)

Bikaner

(n=700)

284

(40.6)

51

(7.3)

65

(9.3)

300

(42.8)

Dehradun

(n=797)

472

(59.2)

85

(10.7)

23

(2.9)

217

(27.2)

Jhansi

(n=855)

318

(37.2)

226

(26.4)

76

(8.9)

235

(27.5)

Kangra

(n=746)

629

(84.3)

24

(3.2)

68

(9.1)

25

(3.4)

New Delhi (IHE)

(n=887)

350

(39.5)

163

(18.4)

82

(9.2)

292

(32.9)

Udham Singh Nagar (n=736)

543

(73.8)

76

(10.3)

25

(3.4)

92

(12.5)

New Delhi (AIIMS)

(n=881)

443

(50.3)

199

(22.6)

35

(3.9)

204

(23.2)

Total

(n=6302)

3505

(55.6)

824

(13.1)

400

(6.3)

1573

(25.0)

a* = Iodine content 15 ppm and more by IT method as well as STK method

b* = Iodine content less than 15 ppm by IT method but 15 ppm and more  by STK method

c* = Iodine content 15 ppm and more by IT method but less than 15 ppm by STK method

d* = Iodie content less than 15 ppm by IT method as well as STK method

 

 

 

Table 5

 

5.1   Sensitivity and Specificity of STK against IT method at Baroda Centre

 

Principal Investigator :          Prof. S. Seshadri

                                                Head, Deptt. of Fods & Nutrition

                                                Faculty of Home Science

                                                M.S. University of Baroda,

                                                Baroda-390002.

 

Sensitivity and Specificity of STK against IT method

 (n=700)

                       

                    Titration Method

STK Method

15 ppm & more

<15 ppm

Total

15 ppm & more

466

0

466

<15 ppm

26

208

234

Total

492

208

700

 

 

Sensitivity                        =        466/492 X100           =          94.7%

 

Specificity                                          =          208/208 X 100          =          100.0%

 

Positive Predictive Value                 =          466/466 X 100          =          100.0%

 

Negative Predictive Value               =          208/234 X 100          =          88.1%

 


 

5.2   Sensitivity and Specificity of STK against IT method at Bikaner Centre

 

Principal Investigator            :           Dr. S.S. Swami

                                                            Deptt. of Preventive and Social Medicine

                                                            Sardar Patel Medical College

                                                            Bikaner- 334003

 

Sensitivity and  Specificity of STK against IT method

 (n=700)

 

                    Titration Method

STK Method

15 ppm & more

<15 ppm

Total

15 ppm & more

284

51

335

<15 ppm

65

300

365

Total

349

351

700

 

 

Sensitivity                                 =        284/349 X 100 = 81.4%

 

Specificity                                 =        300/351 X 100 = 85.5%

 

Positive Predictive Value            =        284/335 X 100 = 64.8%

 

Negative Predictive Value =        300/365 X 100 = 82.2%

 


 

5.3  Sensitivity and Specificity of STK against IT method at Dehradun

       Centre

 

Principal Investigator        :         Ms. Beena

                                                Mamta Samajik Sanstha

                                                UNICEF Sponsored Programme

                                                S3-C- Rajpur Road

                                                Dehradun-248001

 

 

Sensitivity and Specificity of STK against IT Method

 (n=797)

 

                    Titration Method

STK Method

15 ppm & more

<15 ppm

Total

15 ppm & more

472

85

557

<15 ppm

23

217

240

Total

495

302

797

 

Sensitivity                                 =        472/495 X 100 = 95.4%

 

Specificity                                 =        217/302 X 100 = 71.8%

 

Positive Predictive Value            =        472/557 X 100 = 84.7%

 

Negative Predictive Value =        217/240 X 100 = 90.4%

 


 

5.4  Sensitivity and Specificity of STK against IT method at Jhansi Centre

 

Principal Investigator        :         Dr. B.P. Mathur

                                                Reader, Deapartment of PSM,

                                                Medical College,

                                                Jhansi (Uttar Pradesh)

 

Sensitivity and Specificity of STK against IT method

 (n=855)

 

                    Titration Method

STK Method

15 ppm & more

<15 ppm

Total

15 ppm & more

318

226

544

<15 ppm

76

235

311

Total

394

461

855

 

Sensitivity                                                     =        318/394 X 100 = 80.7%

 

Specificity                                                    =        235/461 X 100 = 50.9%

 

Positive Predictive Value                               =        318/544 X 100 = 58.4%

 

Negative Predictive Value                     =        235/311 X 100 = 75.6%

 

 


 

5.5     Sensitivity and Specificity of STK against IT method at Kangra Centre

 

Principal Investigator        :         Dr. T.D. Dharma

                                                Principal

                                                Health & Family Welfare Centre

                                                Kangra- 176001

 

Sensitivity and Specificity of STK against IT method

 (n=746)

 

                    Titration Method

STK Method

15 ppm & more

<15 ppm

Total

15 ppm & more

629

24

653

<15 ppm

68

25

93

Total

697

49

746

 

Sensitivity                                           =        629/697 X 100 = 90.2%

 

Specificity                                          =        25/49 X 100 = 51.0%

 

Positive Predictive Value                      =        629/653 X 100 = 96.3%

 

Negative Predictive Value           =        25/93 X 100 = 26.8%

 


5.6  Sensitivity and Specificity of STK against IT method at New Delhi (IHE) Centre

 

Principal Investigators: Dr. Kumud Khanna and Dr. Amita Attle

                                      Department of Foods and Nutrition,

                                      Institute of Home Economics (IHE),

                                      New Delhi

 

Sensitivity and Specificity of STK against IT method

 (n=887)

 

                    Titration Method

STK Method

15 ppm & more

<15 ppm

Total

15 ppm & more

350

163

513

<15 ppm

82

292

374

Total

432

455

887

 

Sensitivity                                           =        350/432 X 100 = 81.0%

 

Specificity                                          =        292/455 X 100 = 64.2%

 

Positive Predictive Value            =        350/513 X 100 = 68.2%

 

Negative Predictive Value           =        292/374 X 100 = 78.1%


 

5.7     Sensitivity and Specificity of STK against IT method at Udham    Singh Nagar Centre

 

 

Principal Investigator :      Dr. R.S. Raghuvanshi

                                      Reader, Deptt. of Foods & Nutrition

                                      College of Home Science

                                      GB Pant University of Agriculture

                                      and Technology,

                                      Pantnagar, Udham Singh Nagar-263145

 

 

Sensitivity and Specificity of STK against IT method

 (n=736)

 

                    Titration Method

STK Method

15 ppm & more

<15 ppm

Total

15 ppm & more

543

76

619

<15 ppm

25

92

117

Total

568

168

736

 

Sensitivity                                 =        543/568 X 100       = 95.5%

 

Specificity                                 =        92/168 X 100         = 54.7%

 

Positive Predictive Value            =        543/619 X 100       = 87.7%

 

Negative Predictive Value =        92/117 X 100         = 78.6%

             


 

5.8  Sensitivity and Specificity of STK against IT method at New Delhi (AIIMS) Centre

 

Principal Investigator        :         Dr. Umesh Kapil and Dr. S.N. Dwivedi

                                                Additional Professor,

                                                Department of Human Nutrition and

                                                Biostatistics,

                                                All India Institute of Medical Sciences,

                                                Ansari Nagar, New Delhi-110029

 

Sensitivity and Specificity of STK against IT method

 (n=881)

 

                    Titration Method

STK Method

15 ppm & more

<15 ppm

Total

15 ppm & more

443

199

642

<15 ppm

35

204

239

Total

478

403

881

 

Sensitivity                                 =        443/478 X 100       =        92.7%

 

Specificity                                 =        204/404 X 100       =        50.5%

 

Positive Predictive Value            =        443/642 X 100       =        69.0%

 

Negative Predictive Value =        204/239 X 100       =        85.3%

 


 

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