Hemoglobin level and macular thinning in sickle cell disease

Figures & data

Table 1 Patient characteristics and disease classification of study eyes

	NSR (n=26)	NPSR (n=14)	PSR (n=18)	Total (n=58)
Gender
Male	15	5	14	34
Female	11	9	4	24
Mean age (years)	17.1±4.3	16.9±5.0	19.1±2.7
Genotype
Sbeta Thal	2	0	0	2
SBetaPlus Thal	2	2	0	4
SC	8	4	6	18
SS	14	8	12	34

Note: Data are presented as mean ± SD.

Abbreviations: NSR, no sickle retinopathy; NPSR, nonproliferative sickle retinopathy; PSR, proliferative sickle retinopathy.

Table 2 Comparison of CBC indices between SS and SC genotypes

CBC index	SS (n=34)	SC (n=18)	p-value
Hb most recent	9.0±1.6	12.2±1.5	<0.001^
Hb 2 year low	7.1±1.4	10.4±2.2	<0.001^
Hb 2 year high	10.0±1.4	12.2±1.6	<0.001^
Hb 2 year mean	8.6±1.2	11.5±1.6	<0.001^
MCV most recent	93±13	81±8	<0.001^
MCV 2 year low	85±7	79±9	0.004^
MCV 2 year high	100±14	84±10	<0.001^
MCV 2 year mean	92±11	81±9	<0.001^
Plt most recent	398±78	292±149	0.011^
Plt 2 year low	287±81	249±161	0.351
Plt 2 year high	593±162	375±227	<0.001^
Plt 2 year mean	405±70	292±151	0.007^

Notes: ^statistically significant. Data are presented as mean ± SD.

Abbreviations: CBC, complete blood count; Hb, hemoglobin; MCV, mean corpuscular volume; Plt, platelets.

Table 3 Comparison of OCT parameters between SS and SC genotype

OCT parameters (μm)	SS (n=34)	SC (n=18)	Difference	p-value*
Central subfield	233±19	246±19	13±19	0.022^
Superior inner	312±35	329±17	18±30	0.018
Superior outer	279±25	289±14	10±21	0.067
Temporal inner	292±40	317±17	26±33	0.002^
Temporal outer	250±34	271±17	21±30	0.005^
Inferior inner	313±34	326±15	13±29	0.055
Inferior outer	275±19	275±14	−0.3±17.4	0.950
Nasal inner	315±29	331±15	15±25	0.019^
Nasal outer	300±20	304±17	4±19	0.429
Average thickness	277±21	286±14	9±19	0.110
Macular volume	10.0±0.8	10.3±0.5	0.33±0.68	0.100

Notes: *p-value based on unpaired t-test comparing differences in mean between SS and SC genotypes. ^statistically significant.

Table 4 Comparison of average 2-year low hemoglobin (Hb) in eyes with thinning below the 5th percentile vs those with no thinning (top 95th percentile)

OCT parameters (μm)	Average Hb for those with <5th percentile thinning	Number of eyes	Average Hb for those in top 95% thickness	Number of eyes	p-value
Central subfield	6.8±1.6	9	8.9±2.4	49	0.016^
Superior inner	6.9±2.2	13	9.1±2.3	45	0.005^
Superior outer	7.5±2.0	6	8.7±2.5	51	0.269
Temporal inner	6.4±1.5	12	9.2±2.3	46	<0.001^
Temporal outer	6.0±0.9	10	9.1±2.3	48	<0.001^
Inferior inner	7.5±2.4	10	8.8±2.4	48	0.112
Inferior outer	8.7±2.9	5	8.6±2.4	53	0.899
Nasal inner	6.8±1.6	9	8.9±2.4	49	0.024^
Nasal outer	7.9±2.4	6	8.7±2.4	52	0.471
Average thickness	7.3±2.3	11	8.9±2.4	47	0.043^
Macular volume	7.3±2.3	11	8.9±2.4	47	0.043^

Note: ^statistically significant.

Table 5 Regression model predicting macular thickness based on hemoglobin (Hb) values

Predictor	Temporal inner subfield (microns)				Temporal uuter subfield (microns)
	Unadjusted		Parsimonious		Unadjusted		Parsimonious
	Estimate	95% CI, p-value	Estimate	95% CI, p-value	Estimate	95% CI, p-value	Estimate	95% CI, p-value
Hb most recent	7.9	3.1−12.7, 0.002			6.8	2.5−11.2, 0.003
Hb 2 year low	7.4	3.2−11.6, 0.001	7.4	3.2−11.6, 0.001	6.7	2.9−10.4, 0.001	10.4*	5.9−14.8, <0.001
Hb 2 year high	8.9	2.8−14.912, 0.006			6.8	1.1−12.4, 0.021
Hb 2 year mean	9.0	3.8−14.2, 0.001			7.8	3.1−12.6, 0.002
Parameter	Macular volume (mm^3)				Average thickness (microns)
	Unadjusted		Parsimonious		Unadjusted		Parsimonious
	Estimate	95% CI, p-value	Estimate	95% CI, p-value	Estimate	95% CI, p-value	Estimate	95% CI, p-value
Hb most recent	0.12	−0.004−0.249, 0.057			3.4	−0.104−6.952, 0.057
Hb 2 year low	0.12	0.005−0.229, 0.041	0.12	0.005−0.229, 0.041	3.2	0.127−6.366 0.042	3.2	0.127−6.366, 0.042
Hb 2 year high	0.15	−0.005−0.305, 0.057			4.2	−0.105−8.521, 0.056
Hb 2 year mean	0.15	0.011−0.286, 0.036			4.1	0.303−7.969, 0.036

Note: *Parsimonious model also included MCV and Plt values.