The Diagnostic Effectiveness of Low IGF-1 Combined with a Single Insulin Tolerance Test for the Diagnosis of Growth Hormone Deficiency

Worapimon Lerdrassameethad; Khomsak Srilanchakon

Introduction: Currently, there is no diagnostic gold standard for growth hormone deficiency (GHD). The diagnosis of GHD is based on the current consensus guidelines, which state that an inadequate GH level of 7 ng/mL during two growth hormone stimulation tests (GHSTs) is indicative of GHD. The primary objectives of this study were to assess the sensitivity and specificity of low IGF-1 levels in combination with a single insulin tolerance test (ITT) for diagnosing GHD.

Methods: This cross-sectional study analyzed data from 131 children aged 1-16 years with short stature who underwent GHSTs. We compared the diagnostic value of IGF-1 levels using a cut-off value of ≤ 0, -1 and -2 SD score, along with the results of a single ITT. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and the area under the curve (AUC) were evaluated.

Results: Among the 131 children, 98 (74.8%) had an IGF-1 SDS ≤ -1 (median -2.05, IQR -2.80 to -1.49), while 33 (25.2%) had an IGF-1 SDS level > -1 (median 0.08, IQR -0.70 to -0.46). GHD was diagnosed in 46 patients (46.9%) in IGF-1 SDS ≤ -1 group, and 14 patients (42.4%) in IGF-1 SDS > 1 group. Combining an IGF-1 level of ≤0 SDS, ≤ -1 SDS, or ≤ -2 SDS with the results of a single ITT yielded specificities of 71.1%, 66.7%, and 77.8%, respectively. The area under the curve (AUC) of the receiver operating characteristic (ROC) curve was 0.94, 0.92, and 0.99, respectively.


Variable	Sensitivity (95% CI)	Specitivity (95% CI)	PPV (95% CI)	NPV (95% CI)	ROC area (95% CI)	P-value
IGF-1 ≤ 0 SDs + ITT	94.9 (84.6-98.9)	71.1 (56.9-82.7)	74.0 (60.7-84.6)	94.1 (82.4-98.8)	0.94 (0.89-0.98)	<0.001^‡
IGF-1 > 0 SDs + ITT	100.0	66.7 (28.6-92.3)	80.0 (49.7-95.6)	100.0	0.79 (0.52-1.00)	0.006^‡
IGF-1 ≤ -1 SDs + ITT	94.1 (82.4-98.8)	66.7 (50.5-80.3)	72.7 (58.4-84.1)	92.3 (77.5-98.4)	0.929 (0.87-0.98)	<0.001^‡
IGF-1 > -1 SDs + ITT	100.0	80.0 (55.6-94.0)	81.3 (57.9-94.4)	100.0	0.910 (0.79-1.00)	<0.001^‡
IGF-1 ≤ -2 SDs + ITT	100.0	77.8 (55.4-92.0)	86.2 (70.5-95.2)	100.0	0.99 (0.95-1.00)	<0.001^‡
IGF-1 > -2 SDs + ITT	90.9 (73.9-98.1)	66.7 (49.7-80.8)	64.5 (47.0-79.5)	91.7 (75.9-98.2)	0.84 (0.74-0.95)	<0.001^‡
^‡ P < 0.05 (statistic significant)

Conclusion: When used in combination with the results of a single ITT, low IGF-1 values (≤ 0, ≤ -1, or ≤ -2 SDS) showed suboptimal diagnostic accuracy for GHD.

ESPE Abstracts

P2-148