Table 2.

Validation Studies for Current Nephrolithometric Scoring Systems

Study	Country	N	Preoperative Imaging	Postoperative Imaging	Definition of Stone Free	Clearance by Stone Complexity	Complications by Stone Complexity	Statistical Method
Guy’s Stone Score
Thomas K et al7	United Kingdom	100	CT, radiograph, IVU	KUB radiograph	< 4-mm fragments	Overall, 62%	Not reported; no significant correlation only	Multivariate linear regression analysis
						Grade 1, 81%
						Grade 2, 72.4%
						Grade 3, 35%
						Grade 4, 29%
Mandal S et al11	India	278	Radiograph, IVU, USS, noncontrast CT	KUB radiograph	Complete absence of stones	Overall, 76.1%	Overall, 41.7%	Univariate analysis
						Grade 1, 100%	Grade 1, 4.8%
						Grade 2, 74%	Grade 2, 9.1%
						Grade 3, 56%	Grade 3, 26.2%
						Grade 4, 0%	Grade 4, 44.4%
Vicentini FC et al13	Brazil	147	Noncontrast CT		Asymptomatic fragments < 4 mm	Overall, 71.6%	Overall, 18.7%	Univariate analysis
						Grade 1, 95.2%	Grade 1, 4.8%
						Grade 2, 79.5%	Grade 2, 9.1%
						Grade 3, 59.5%	Grade 3, 26.2%
						Grade 4, 40.7%	Grade 4, 44.4%
Ingimarsson JP et al14	Lebanon	66	Noncontrast CT		No fragments/no fragments > 2 mm/no fragments > 4 mm	Overall, 90%	Not reported; no significant correlation only	Univariate analysis
						Grade 1, 95%
						Grade 2, 97%
						Grade 3, 95%
						Grade 4, 75%
Labadie K et al12	United States	246	CT scan	Unclear	Not defined	Overall, 56%	Overall, 17%	Logistic regression
						Grade 1, 70.2%
						Grade 2, 65.4%
						Grade 3, 48.1%
						Grade 4, 35.9%
Noureldin YA et al27	Canada	185	Unclear	Plain radiographs or non-contrast CT	Asymptomatic residual fragments < 4 mm	Overall, 71.9%	Overall, 16.2%	Logistic regression analysis
						Grade 1, 91.5%	Grade 1, 17%
						Grade 2, 80%	Grade 2, 15%
						Grade 3, 47.6%	Grade 3, 9.5%
						Grade 4, 43.2%	Grade 4, 21.6%
Bozkurt IH et al20	Turkey	437	CT scan	KUB radiograph (unless CT; which is reserved for only symptomatic patients)	Asymptomatic residual fragments < 4 mm	Overall, 75%	Overall, 35%	Linear and logistic regression analyses
						Grade 1, 92.8%	Grade 1, 13.0%
						Grade 2, 72.4%	Grade 2, 2.5%
						Grade 3, 68.5%	Grade 3, 8.7%
						Grade 4, 47.4%	Grade 4, 10.3%
Nephrolithometric Nomogram (CROES)
Smith A et al8	International (CROES PCNL Group)	2806	Unclear	KUB radiograph	No fragments > 4 mm	Overall, 82%	Not reported	Multivariate logistic regression
						Odds ratios and nomogram reported
						ROC AUC 5 0.76
Labadie K et al12	United States	246	CT scan	Unclear	Not defined	Overall, 56%	Overall, 17%	Logistic regression
						80–129 = 22.7%
						130–169 = 46.4%
						170–219 = 45.5%
						≥ 220 = 72.7%
Bozkurt IH et al20	Turkey	437	CT scan	KUB radiograph (unless CT; which is reserved for only symptomatic patients)	Asymptomatic residual fragments < 4 mm	Overall, 75%	Overall, 35%	Linear and logistic regression analyses
						Grade 1, 48.5%	Grade 1, 4.8%
						Grade 2, 51.4%	Grade 2, 8.0%
						Grade 3, 69.1%	Grade 3, 7.5%
						Grade 4, 92.8%	Grade 4, 14.2%
S.T.O.N.E. Nephrolithometry
Okhunov Z et al9	United States	117	Noncontrast CT	Fluoroscopy ± CT	Complete absence of stones on CT	Overall, 80%	Not reported	Multivariate logistic regression
						Low (4–5), 94%–100%; medium (6–8), 83%–92%; high (9–11), 27%–64%;
						ROC AUC = 0.83
Okhunov Z et al24	United States	58	Noncontrast CT	Fluoroscopy ± CT	N/Aa	N/Aa	N/Aa	Cohen’s kappa coefficienta
Okhunov Z et al26	United States	706	CT scan	Unclear	Not defined	Overall 67%	S.T.O.N.E. score significantly associated with overall complication rate	Univariate analysis
						S.T.O.N.E. score significantly associated with postoperative SFS
Labadie K et al12	United States	246	CT scan	Unclear	Not defined	Overall, 56%	Overall, 17%	Logistic regression
						5–6 5 70.6%
						7–8 5 66.3%
						9–13 5 46.2%
						ROC AUC = 0.67
Akhavein A et al25	United States	122	CT scan		Residual fragments < 4 mm	Score vs clearance %:	Score vs complication %:	Univariate analysis and logistic regression
						5–7 = 100%	5 = 0%
						8 = 80%	6 = 1.6%
						9 = 94.1%	7–8 = 0%
						10 = 79.2%	9 = 0.8%
						11 = 66.7%	10 = 6.6%
						12 = 45%	11–12 = 0%
Noureldin YA et al27	Canada	185	Unclear	Plain radiographs or noncontrast CT	Asymptomatic residual fragments < 4 mm	Overall, 71.9%	Overall, 16.2%	Logistic regression analysis
						5 = 100%	5 = 20%
						6 = 75%	6 = 18.2%
						7 = 77.3%	7 = 11.4%
						8 = 67.6%	8 = 20.6%
						9 = 79.3%	9 = 20.7%
						10 = 58.3%	10 = 8.3%
						11 = 42.9%	11 = 0%
						12–13 = 0%	12 = 25%
							13 = 0%
Noureldin YA et al28	Canada	155	Noncontrast CT	KUB and/or non-contrast CT	Residual stones ≥ 4 mm considered as non-stone-free	Overall, 71.6%	Overall, 15.5%	Multivariate logistic regression
						Significant inverse association between S.T.O.N.E. score and clearance AUC = 0.63	No correlation between S.T.O.N.E. score and complications
Seoul Renal Stone Complexity Score
Jeong CW et al10	South Korea	155	Noncontrast CT		No evidence of residual stones on postop images after 1 mo	Overall, 72.3%	Overall, 25.2%	Univariate analysis; ROCs
						Low (1–2), 96%; medium (3–4), 69%; high (5–9), 28%	Low (1–2), 1.9%; medium (3–4), 28.6%; high (5–9), 34.2%
Choo MS et al31	South Korea	327	Noncontrast CT		Complete clearance/clearance with clinically insignificant residual fragments (4 mm) at 1 mo follow-up imaging	Overall, 65.4%	Not investigated	Univariate and multivariate regression analyses; ROCs
						Low (1–2), 83.9%; medium (3–4), 47.6%; high (5–9), 21.4%
Park J et al32	South Korea	159	Unclear		No evidence of a stone or with clinically insignificant residual fragment stones < 2 mm	Overall, 73.0%	Not investigated	Uni- and multivariate linear regression
						Low (1–2), 86.7%; medium (3–4), 70.2%; high (5–12), 48.6%

^aStudy focuses on interobserver reliability.

AUC, area under the curve; CT, computed tomography; IVU, intravenous urogram; KUB, kidneys, ureters, and bladder; ROC, receiver operating characteristic; SFS, stone-free status; S.T.O.N.E., stone size, tract length, obstruction, number of involved calices, and essence/stone density; USS, abdominal and pelvic ultrasound.