Table 2.
Test Characteristics of Selected HC Thresholds for Diagnosis of Children with IEC or MGCM
| A | B | C | D | E | G | H | I | K | L | M | N |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Threshold | Number in source population | Number diagnosed with IEC or MGCM | Number above threshold | Number above threshold with IEC or MGCM |
Sensitivity E/C |
Specificity (B-C-(D-E))/(B-C) |
Positive predictive value E/D |
Likelihood ratio positive G/(1-H) |
Likelihood ratio negative (1-G)/H |
Number Needed to Screen B/E |
Number Needed to Test D/E |
| Above CDC 95th | 74,428 | 85 | 12,325 | 39 | 46% | 83% | 0.3% | 2.8 | 0.6 | 1,908 | 316 |
| Above WHO 95th | 74,428 | 85 | 18,528 | 47 | 55% | 75% | 0.3% | 2.2 | 0.6 | 1,584 | 394 |
| Above PCN 95th | 74,428 | 85 | 7,694 | 34 | 40% | 90% | 0.4% | 3.9 | 0.7 | 2,189 | 226 |
| Above CDC 97th | 74,428 | 85 | 8,373 | 34 | 40% | 89% | 0.4% | 3.6 | 0.7 | 2,189 | 246 |
| Above WHO 97th | 74,428 | 85 | 13,275 | 41 | 48% | 82% | 0.3% | 2.7 | 0.6 | 1,815 | 324 |
| Above PCN 97th | 74,428 | 85 | 4,532 | 29 | 34% | 94% | 0.6% | 5.6 | 0.7 | 2,566 | 156 |
| Above CDC 99.6th | 74,428 | 85 | 2,030 | 20 | 24% | 97% | 1.0% | 8.7 | 0.8 | 3,721 | 102 |
| Above WHO 99.6th | 74,428 | 85 | 3,438 | 25 | 29% | 95% | 0.7% | 6.4 | 0.7 | 2,977 | 138 |
| Above PCN 99.6th | 74,428 | 85 | 711 | 13 | 15% | 99% | 1.8% | 16.3 | 0.9 | 5,725 | 55 |
| Crossed 2 IMPL-CDC | 64,015 | 83 | 29,206 | 50 | 60% | 54% | 0.2% | 1.3 | 0.7 | 1,280 | 584 |
| Crossed 2 IMPL-WHO | 64,015 | 83 | 22,462 | 33 | 40% | 65% | 0.1% | 1.1 | 0.9 | 1,940 | 681 |
| Crossed 2 IMPL-PCN | 64,015 | 83 | 13,831 | 26 | 31% | 78% | 0.2% | 1.5 | 0.9 | 2,462 | 532 |
| Crossed 4 IMPL-CDC | 64,015 | 83 | 5,727 | 13 | 16% | 91% | 0.2% | 1.8 | 0.9 | 4,924 | 441 |
| Crossed 4 IMPL-WHO | 64,015 | 83 | 4,372 | 7 | 8% | 93% | 0.2% | 1.2 | 1.0 | 9,145 | 625 |
| Crossed 4 IMPL-PCN | 64,015 | 83 | 1,703 | 6 | 7% | 97% | 0.4% | 2.7 | 1.0 | 10,669 | 284 |
IEC (intracranial expansive condition); MGCM (metabolic or genetic condition associated with macrocephaly); CDC (Centers for Disease Control head circumference growth curves); WHO (World Health Organization head circumference growth curves); PCN (primary care network head circumference growth curves); IMPL (multiple percentile lines). The negative predictive value (C-(D-E))/(C-D) was 99.9% for all thresholds. No subjects with the outcome crossed 6 increasing MPL, so rows for that outcome were not included. Point estimates and 95% confidence intervals are presented for the thresholds with the highest and lowest sensitivity and highest positive predictive value. The sensitivity of crossing 2 IMPL on the CDC curve for detecting children with IEC or MGCM who received intervention was 78% (95% CI: 56%, 93%). The sensitivity of crossing 4 IMPL on the PCN curve for detecting children with IEC or MGCM was 7% (95% CI: 3%, 15%). The positive predictive value of ever being above the 99.6th percentile of the PCN curve for detecting children with IEC or MGCM was 1.8% (95% CI: 1.0%, 3.1%).