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 Table of Contents  
ORIGINAL ARTICLE
Year : 2019  |  Volume : 16  |  Issue : 2  |  Page : 76-79

Cord blood thyroid-stimulating hormone as a screening tool for congenital hypothyroidism: A single-center 5-year experience


Department of Pediatrics, Pacific Medical College and Hospital, Udaipur, Rajasthan, India

Date of Web Publication15-Jul-2019

Correspondence Address:
Dr. Ravi Bhatia
Associate Professor, Department of Pediatrics, Pacific Medical College and Hospital, Udaipur - 313 002, Rajasthan
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/trp.trp_15_19

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  Abstract 


Introduction: Congenital hypothyroidism remains one of the most common preventable causes of mental retardation in the pediatric age group. Screening for congenital hypothyroidism is one of the most cost-effective tools to prevent mental retardation among the general population. Umbilical cord blood thyroid-stimulating hormone (CB TSH) estimation remains an easily available option for screening for congenital hypothyroidism.
Aim: The aim of this study was to find normative values of CB TSH for the study group and to use CB TSH levels as a screening tool for congenital hypothyroidism.
Design: This study was a cross-sectional study.
Setting: This study was conducted in a private medical college.
Materials and Methods: CB TSH levels were measured in 2916 neonates using chemiluminescence immunoassay. All neonates who had an umbilical CB TSH level >20 mIU/ml were called back on day 7 for a repeat thyroid profile testing.
Results: CB samples of 3102 neonates were tested for TSH; of them, 186 samples were hemolyzed, and hence, 2916 neonates formed the study group. Male-to-female ratio was 1544:1378, i.e., 1.2.1. The birth weights of the study group ranged between 0.8 kg and 4.76 kg, with the average birth weight being 2.9 kg. The cohort was divided into two groups: Group 1 (n = 1983) comprised of neonates who were born term and Group 2 (n = 933) comprised of neonates who were born before term gestation. TSH values ranged between 1.2 and 100 mIU/ml. The mean TSH value of the cohort was 7.17 mIU/ml. The mean TSH value in Group 1 was 6.89 mIU/ml, whereas in the Group 2, it was 7.57 mIU/ml. TSH values corresponding to the 3rd, 10th, 25th, 50th, 75th, 90th, 95th, and 97th percentile were 2.3, 2.9, 3.48, 5.4, 7.1, 10.67, 13.4, and 21.4, respectively, in Group 1, whereas TSH values corresponding to the 3rd, 10th, 25th, 50th, 75th, 90th, 95th, and 97th percentile in Group 2 were 2.32, 3.12, 4.12, 5.63, 7.65, 10.67, 13.4, and 22, respectively. Seventy neonates (2.4%) had a CB TSH value >20 mIU/ml and had to be recalled for a repeat workup. Of the 70 babies recalled for repeat testing, 59 turned up and eventually two turned out to be hypothyroid on repeat testing. The incidence of congenital hypothyroidism in our study was 1 in 1458. To conclude, we can safely use a cutoff of CB TSH >20 mIU/ml for screening for congenital hypothyroidism.
Conclusion: A cut off Cord Blood TSH value > 20 IU/ml can be used for screening purpose.

Keywords: Congenital hypothyroidism, screening, umbilical cord blood TSH value


How to cite this article:
Bhatia R, Rajwaniya D. Cord blood thyroid-stimulating hormone as a screening tool for congenital hypothyroidism: A single-center 5-year experience. Thyroid Res Pract 2019;16:76-9

How to cite this URL:
Bhatia R, Rajwaniya D. Cord blood thyroid-stimulating hormone as a screening tool for congenital hypothyroidism: A single-center 5-year experience. Thyroid Res Pract [serial online] 2019 [cited 2019 Aug 21];16:76-9. Available from: http://www.thetrp.net/text.asp?2019/16/2/76/262727




  Introduction Top


Congenital hypothyroidism is one of the most common causes of preventable mental retardation in the country. Various studies across India have found the incidence of congenital hypothyroidism to range between 1 in 4000 and 1 in 2500 births in India.[1] In India, there is widespread variation in the incidence of congenital hypothyroidism, with figures as high as 1:500 in Kochi to figures as low as 1:3400 in Chandigarh.[2],[3],[4] The reason for this widespread variability is a lack of pan-India studies which have used cord blood thyroid-stimulating hormone (CB TSH) as a screening marker.

Since clinical features of congenital hypothyroidism are mostly nonspecific, screening at birth assumes paramount importance. Screening for congenital hypothyroidism remains one of the most important cost-effective tools in preventing mental retardation in the population. Neonatal screening programs for congenital hypothyroidism screening are widespread in developed countries, but unfortunately, a nationwide program is still nonexistent in our country. Ideally screening for Congenital Hypothyroidism should be done after the TSH surge is over i.e. at 72 hrs of life but in our country many babies are discharged early hence cord blood TSH comes across as an easily available alternative. Many neonatologists remain skeptical of using CB TSH as a screening tool for screening for congenital hypothyroidism as it is widely influenced by antenatal and perinatal factors. Various Asian nations are using CB samples for screening for congenital hypothyroidism.[5],[6],[7],[8] Few studies across India have used CB TSH as a screening tool for congenital hypothyroidism.[9],[10],[11] This study was planned to find normative values of TSH in CB samples and to use CB TSH as a screening marker for congenital hypothyroidism.

Aim

  1. To find the normative values of CB TSH for the study group
  2. To use CB TSH as a screening marker for congenital hypothyroidism.



  Materials and Methods Top


This cross-sectional study was carried out from January 2014 to January 2019 in a private medical college located in Southern Rajasthan. Prior approval from the Institutional Ethics Committee was sought before starting the study. All consecutive deliveries conducted during this period were a part of the study. All the deliveries were attended by either of the two authors. Exclusion criteria were neonates with major congenital malformations, neonates requiring resuscitation at birth, neonates requiring neonatal intensive care unit admission, neonates with gestational age <28 weeks at birth, and neonates whose mothers were on antithyroid medications. Detailed antenatal history, parity, medical history, thyroid status of the mother, gestational age, birth weight of baby, etc., were recorded on a predesigned per forma. Umbilical cord was clamped using three clamp techniques: one close to the baby and two near the placental end after cessations of pulsations. 5 ml blood was collected in a sterile plain vial at the time of delivery, and the sample was subjected to TSH estimation by chemiluminescence immunoassay method (kit supplied by Roche E411). CB TSH samples of 3102 neonates were sent for estimation. All neonates who had a CB TSH value >20 mIU/ml were called back on day 7 of life for a full thyroid profile, including TSH, T3, T4, fT3, and fT4. Repeat TSH level >20 mIU/ml was considered confirmatory for congenital hypothyroidism. The data were entered on an excel worksheet and analyzed using SSPS software for windows version 12 (IBM, SPSS, India).


  Results Top


CB samples of 3102 neonates were sent for TSH estimation; of them, 186 samples were hemolyzed and were excluded from the study. A total of 2916 neonates formed the study group. Male-to-female ratio was 1544:1378, i.e., 1.2:1 [Table 1]. The birth weights of the study group ranged between 0.8 kg and 4.76 kg. The average birth weight was 2.9 kg. [Table 2] depicts the weight-wise distribution of the entire cohort. The study group was divided into two further groups: Group 1 comprised of babies who were born at term (n = 1983, 68% of the total neonates) and Group 2 included babies who were born preterm, i.e., before 37 weeks of gestation (n = 933, 32% of total neonates) [Table 3]. The mean TSH value of the entire cohort was 7.17 mIU/ml. The mean TSH value in Group 1 was 6.89 mIU/ml, whereas in the Group 2, it was 7.57 mIU/ml. TSH values ranged between 1.2 and 100 mIU/ml [Table 4]. TSH values corresponding to the 3rd, 10th, 25th, 50th, 75th, 90th, 95th, and 97th percentile were 2.3, 2.9, 3.48, 5.4, 7.1, 10.67, 13.4, and 21.4, respectively, in the Group 1, whereas TSH values corresponding to the 3rd, 10th, 25th, 50th, 75th, 90th, 95th, and 97th percentile in Group 2 were 2.32, 3.12, 4.12, 5.63, 7.65, 10.67, 13.4, and 22, respectively. Seventy neonates were recalled for repeat testing, i.e., a recall rate of 2.4%. Among the 70 neonates who were called for repeat testing, 59 turned up and 11 were lost to follow-up. Two neonates of the cohort who were called up for repeat testing turned out to be suffering from congenital hypothyroidism.
Table 1: Gender-wise distribution (n=2916)

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Table 2: Distribution of weight at the time of birth (n=2916)

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Table 3: Distribution according to gestational age (n=2916)

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Table 4: Distribution of cord blood thyroid-stimulating hormone values (n=2916)

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  Discussion Top


Screening for congenital hypothyroidism is the need of the hour as it would lead to early detection of mental retardation and decrease the burden of mentally retarded children in the society. Unfortunately, it has not been implanted in our country as a nationwide program due to lack of available facilities, cost burden, and lack of awareness among treating physicians. The method of screening for congenital hypothyroidism is not uniform; some centers use T4 as a screening tool, whereas others use TSH. Ideally, both TSH and T4 should be used for screening for congenital hypothyroidism but that would increase the cost burden. Umbilical CB TSH as a marker for screening for congenital hypothyroidism is easily available and is a practical alternative to heel prick sample as far as screening for congenital hypothyroidism is concerned. Studies across the world have shown that CB TSH remains a good alternative for screening for congenital hypothyroidism. In our study, 7.5% of the samples had a CB TSH value >10 mIU/ml which is quite similar to that reported by Mekenon et al.[12] and Manglik et al.[9] The mean TSH value of our cohort was 7.17 mIU/ml which is quite similar to that as reported by other authors. Our recall rate for repeat testing was 2.4% which is quite similar to 2.27% as reported by Wu et al.[8] who had a large cohort of 11000 neonates. Manglik et al.[9] have reported a recall rate of 1.833%, but their sample size is less as compared to our study, and they have included only term neonates. Another study from our state has a recall rate of 5.57%[11] which is quite high as compared to other studies across the world. There is no universally accepted cutoff for CB TSH level as far as screening purpose is concerned. Many researchers have used a cutoff of 20 mIU/ml for screening. Had we used a cutoff of 30 mIU/ml, our recall rate would have fallen to 1.92%, and on further increasing the cutoff to 40 mIU/ml, our recall rate would have fallen to 1.33%. Considering our annual birth rate of 20 million babies and a recall rate of 2.4%, almost 480,000 babies would need to be called back for repeat testing. It would indeed be a herculean task and would pose a big challenge to our health-care system. Higher cutoff values of TSH for recall would lead to lesser babies being called for repeat testing, thereby decreasing the burden on our health-care systems.

We had two babies with congenital hypothyroidism in a cohort of 2916 giving us an incidence of 1 in 1458. We had earlier reported an incidence of 1 in 1824 but that study included only term neonates. Another study from our state has reported an incidence of 1 in 1370.[11] Various studies across India have reported the incidence of congenital hypothyroidism as varied as between 1 in 248 and 1 in 1700.[13],[14] Geographic, demographic, ethnic, and racial factors; sample size; and cutoff used for screening are all known to influence the incidence of the disease.

Our figures have shown a comparable trend with normative data for CB TSH values as reported by various workers across the globe.

The biggest drawback of our study is in spite of it being a five year project the sample size is relatively small as the number of deliveries are less due to it being a private college. However, large population-based studies are required to gauge and calculate the incidence of congenital hypothyroidism in our country.


  Conclusion Top


The incidence of congenital hypothyroidism is much higher in Indian as compared to other countries across the globe. Delay in diagnosis can lead to lifetime intellectual impairment. Umbilical CB TSH is a practical and an easily available alternative for screening for congenital hypothyroidism in our country. We can safely use a cutoff of CB TSH value of >20 mIU/ml for the purpose of screening for congenital hypothyroidism. However, large population-based studies are required for establishing normative values for CB TSH across the country.

Acknowledgment

The authors are grateful to Prof. AP Gupta, Dean, Pacific Medical College and Hospital, Udaipur, for allowing us to conduct the study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Desai MP, Colaco MP, Ajgaonkar AR, Mahadik CV, Vas FE, Rege C, et al. Neonatal screening for congenital hypothyroidism in a developing country: Problems and strategies. Indian J Pediatr 1987;54:571-81.  Back to cited text no. 1
    
2.
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Singh Ra, Devi KG, Devi Kl, Bainik U. Newborn screening for congenital hypothyroidism in Manipur by measurement of umbilical cord thyroid stimulating hormone: A hospital based study. J Med Soc 2013;27:127-30.  Back to cited text no. 3
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Fagela-Domingo C, Padilla CD, Cutiongco EM. Screening for congenital hypothyroidism (CH) among Filipino newborn infants. Philippine newborn screening study group. Southeast Asian J Trop Med Public Health 1999;30 Suppl 2:20-2.  Back to cited text no. 5
    
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Azizi F, Oladi B, Nafarabadi M, Hajipur R. Screening for congenital hypothyroidism in Tehran: The effect of iodine deficiency on transient elevation of TSH in neonates. J Fac Med SBUMS 1993;18:34-8.  Back to cited text no. 6
    
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Wu LL, Sazali BS, Adeeb N, Khalid BA. Congenital hypothyroid screening using cord blood TSH. Singapore Med J 1999;40:23-6.  Back to cited text no. 8
    
9.
Manglik AK, Chatterjee N, Ghosh G. Umbilical cord blood TSH levels in term neonates: A screening tool for congenital hypothyroidism. Indian Pediatr 2005;42:1029-32.  Back to cited text no. 9
    
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Bhatia R, Rajwaniya D. Congenital hypothyroidism screening in term neonates using umbilical cord blood TSH values. Indian J Endocrinol Metab 2018;22:277-9.  Back to cited text no. 10
    
11.
Chaudhary M, Soni JP, Goyal VK, Sharma P, Makwana M, Lora SS, et al. Incidence of congenital hypothyroidism in western Rajasthan using cord blood thyroid-stimulating hormone levels as a screening tool: A cross-sectional hospital-based study. Indian J Endocrinol Metab 2018;22:417-20.  Back to cited text no. 11
    
12.
Mekennon Y, Gizachew WH, Chamiso B, Raue F. Thyroid stimulating hormone values in cord blood in neonates. Ethiop J Health Dev 2003; 17:125-30.  Back to cited text no. 12
    
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Khadilkar V, Khadilkar A, Cowasji H. Neonatal thyroid screening program using filter paper method. Cape News 2002;6:1.  Back to cited text no. 13
    
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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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