A strategy to avoid missed cases in a Brazilian neonatal TSH screening program for congenital hypothyroidism

Epidemiological profile of congenital hypothyroidism at a southern Brazilian state

Objective

To determine the incidence of congenital hypothyroidism (CH) over a 10-year period at the Reference Service in Neonatal Screening of the state of Rio Grande do Sul (RSNS-RS).

Subjects and methods

Historical cohort study including all newborns screened for CH by the RSNS-RS from January 2008 until December 2017. Data of all newborns with neonatal TSH (neoTSH; heel prick test) values ≥ 9 mIU/L were collected. According to neoTSH values, the newborns were allocated into two groups: Group 1 (G1), comprising newborns with neoTSH ≥ 9 mIU/L and serum TSH (sTSH) < 10 mIU/L, and Group 2 (G2), comprising those with neoTSH ≥ 9 mIU/L and sTSH ≥ 10 mIU/L.

Results

Of 1,043,565 newborns screened, 829 (0.08%) had neoTSH values ≥ 9 mIU/L. Of these, 284 (39.3%) had sTSH values < 10 mIU/L and were allocated to the G1 group, while 439 (60.7%) had sTSH ≥ 10 mIU/L and were allocated to the G2 group, and 106 (12.7%) were considered missing data. The overall incidence of CH was 42.1 per 100,000 newborns screened (95% confidence interval [CI] 38.5-45.7/100,000) or 1:2377 screened newborns. The sensibility and specificity of neoTSH ≥ 9 mIU/L were 97% and 11%; of neoTSH 12.6 mUI/L, 73% and 85% respectively.

Conclusion

In this population, the incidence of permanent and transitory CH was 1:2377 screened newborns. The neoTSH cutoff value adopted during the study period showed excellent sensibility, which matters for a screening test.

Determining the TSH reference range in national newborn screening program for congenital hypothyroidism

Objective: Since the initiation of the thyroid screening program in Iran in 2005, 5 mIU/L has been selected as the threshold for thyroid stimulating hormone (TSH) for screening for congenital hypothyroidism. Given the specific disease pattern in the region and current controversies of the TSH cutoff point, a new cutoff point has been proposed in this study.Methods: This study was conducted on the existing database of the screening program consisting of 127,112 neonates in Markazi Province, center of Iran, during 2006-2012. Data on 614 referred neonates consisting of 414 neonates diagnosed of having hypothyroidism and 200 screened healthy neonates, were analyzed. The heel prick test had been done on the studied neonates to determine the TSH levels. The receiver-operator characteristic (ROC) curve and diagnostic values were used for data analysis.Results: The 5-mIU/L cutoff point in the study had a sensitivity and specificity and AUC of 86.5, 10 and 47%, respectively. Among the eleven selected cutoff points, 6.5 mIU/L had the appropriate sensitivity, specificity and AUC (58.9, 56.5 and 57%, respectively), negative and positive likelihood ratios (0.73 and 1.35, respectively).Conclusion: Given the very low specificity of the 5-mIU/L cutoff point for referral and with respect to the high rate of referrals and many false positive cases, we suggest to use the 6.5-mIU/L cutoff point which is more suitable.

Worldwide Recall Rate in Newborn Screening Programs for Congenital Hypothyroidism

CONTEXT

Neonatal mass screening program for congenital hypothyroidism provides the best tool for prevention of its devastating effects on mental development. Despite the overall success of the screening programs in detecting congenital hypothyroidism and eliminating its sequelae and new developments made in the program design, high recall rate and false positive results impose a great challenge worldwide. Lower recall rate and false positive results may properly organize project expenses by reducing the unnecessary repeated laboratory tests, increase physicians and parents' assurance and cooperation, as well as reduce the psychological effects in families.

EVIDENCE ACQUISITION

In this review, we assessed the recall rate in different programs and its risk factors worldwide.

METHODS

Publications reporting the results of the CH screening program from 1997 to 2016 focusing on the recall rate have been searched.

RESULTS

Recall rates vary from 0.01% to 13.3% in different programs; this wide range may be due to different protocols of screening (use of T4 or TSH or both), different laboratory techniques, site of sample collection, recall cutoff, iodine status, human error, and even CH incidence as affected by social, cultural, and regional factors of the population.

CONCLUSIONS

It is suggested to implement suitable interventions to reduce the contributing factors by improving the quality of laboratory tests, selecting conservative cut off points, control iodine deficiency, use of iodine free antiseptic during delivery, and use of more specific markers or molecular tests. Applying an age dependent criteria for thyrotropin levels can be helpful in regions with a varied time of discharge after delivery or for preterm babies.